I left the post stand despite a report, but OP appears to be sealioning in the comments, so...locking.

wisdom at 18? fuck me, im 61 and the only thing I'm certain about is that humanity, myself included in that venn diagram, lacks any wisdom at all.

Because many adults don't acknowledge that they are a part of their kids' learning expperience.

They assume that kids will magically become smarter the second they turn 18, and don't understand that kids have to be exposed to information and some adversity before then (ideally with guidance from parents) to learn enough.

Social media is very addictive, because it's designed that way... so let's regulate the social media and their intentionally addictive practices, rather than blaming kids and ripping them away from some of the only "socialization" our society allows kids to have.

"Go bike to your friend's house" doesn't work, because the last two generations have built eight-game highways everywhere.

You dont appreciate how stupid you were until you are older. Then you realize you were stupid when you were younger, and are stupid now, but over different things. If this isnt a persons experience in life, they are almost certainly a Republican. (Joke... Mostly)

This is because with a lot of things in life, you have to actually experience them to figure out if and how you could have handled it better. You dont regret everything you do, but the things you eff up, stick with you...

Former stupid kid, current stupid middle ager.

The screens are designed to be addicting. That's not hyperbole. They literally use data scientists to increase the amount of time and money you spend on them. The longer you scroll, the more time you're playing the game, the more money the developers make on average. Online service providers don't care about your wellbeing. Your parents do. Just like there's more food than chips and cake, there's more to life than being on a screen. Investing in long term hobbies, skills, and friendships won't have the instant gratification to compete with a video game, but 10 years from now you will think back way more fondly on your hours skateboarding or learning to play guitar than the ones you lost online.

Part of it is arrogant bullshit stemming from a complete inability to accurately remember what the experience of being young was like. Most people suck ass at honest self-assessment at every stage of life, so they fall into the trap of thinking they and their cohort were different than "kids these days" and are unable to empathize with or relate to young people because of this.

Part of it is that kids genuinely just aren't fully developed neurologically, in ways that frequently lead to making shortsighted decisions with negative results. Unfortunately that's still true way past 18, it's an arbitrary threshold and the expectation that people should instantly stop acting childish at 18 is just as stupid as assuming that anyone younger than 18 is categorically incapable of making the right decisions for themselves.

The specific examples you're using have some reasonable claim to option 2 depending on the context. Even as adults most people struggle to some degree with eating healthy nutritionally balanced diets, and children generally have less self-discipline so it can be more of a problem for them. Forcing kids to eat things they don't want is a bad idea though, you'll just give them a complex about eating and make them hate that specific food forever. My parents rule was that I never had to finish anything I didn't like, but I had to try at least one bite of everything before deciding I didn't like it. Worked like a charm, I eat everything.

Screen time is similar, plenty of adults struggle with regulating their gaming and social media usage, and the companies that make games and websites get paid more when people use their stuff more, so they have an incentive to design things to be addictive and predatory. Adults assuming that all screen time is bad for kids are stupid, but it is possible that an adult might recognize a predatory system that a child wouldn't have any experience with and save them from being taken advantage of. Best practice is to actually pay attention to what's on your kids' screen and discuss it openly with them. Unfortunately a lot of adults don't want to do that because it's difficult, they default to either assuming all screen time is bad or to not trying at all, so their kids are either needlessly restricted in their growth or exposed to the worst the internet has to offer. Both bad.

Tldr the adults you're dealing with aren't necessarily completely wrong but they're probably still full of shit

Knowledge and wisdom are not the same. Wisdom is knowledge compounded by experience. The examples you list are not wisdom, nor are they necessarily knowledge. They are parenting techniques with obvious flaws.

As for 18 being the magic number, that's pretty societally arbitrary. Sure, one is legally an adult at 18 in many societies, but that doesn't mean they have life experience to amount to having wisdom. Many 18 year olds know enough to function in society, but they're realistically still children from a developmental standpoint. There's no magic age for anything.

..

Because they are.

Hell there is a substantial number of people who stay allergic to wisdom their entire lives.

screen time is just a limit on time to learn if the kid is using it for the right purposes

There is much learning to be had out in the real world also. A balance of the two is important. Limits should be in place if the kid naturally spends too much time on one or the other.

"finish your plate" I was never told that as a kid and I devour anything that is given to me

If you did it on your own, why would anyone ever tell you to do it?

The thing about wisdom is that it requires understanding, which is different from knowing. I can know a rule without understanding the motivation or underlying reasoning of the rule, and crucially, I can still follow the rule even if I don't understand it. This is useful for children because there are a ton of things they don't understand about the world that can hurt them if they're not prepared for it. Take for example the rule: "look both ways before crossing the street". It's a rule that is taught to children because running into a street without looking out for cars can get kids killed. There are a million situations like this. Not all of them are as starkly life and death, but kids who have a good set of rules can move through the world more safely and comfortably than kids without, and they can learn rules faster than they can learn the underlying logic of them. That can and should come later.

There are also rules that aren't so good. I think "make sure you finish your plate no matter what" is a rule that arose from a well-meaning attempt to prevent food waste, but it's a rough fit for the purpose and it can make it hard for children to develop their own understanding of their eating preferences. I wouldn't give a child that rule, I would spend a little more effort coming up with a solution to make sure kids are getting the nutrition they need without resorting to such ham-fisted measures.

Screen time rules are tricky, because we haven't had constant access to screens for very long, and the way we interact with them (TVs to PCs to smartphones, to say nothing of the media landscape in which these devices are situated) is still changing rapidly. Parents are doing their best to keep up and it is overwhelming because nobody really knows what the best rule is. I think it's easy to say "just do whatever's best for your child" if you don't have kids because it's hard to grasp the true scope of the problem of parenting: there are simply too many threats or possible threats to a child's well-being to individually tailor solutions to everything, and you as a parent, have to pick which areas require tailoring and which areas have sufficient rules to fall back on.

I don't think this is unique to children either. There are plenty of domains of knowledge where knowing a few good rules can make life a lot better even if you don't understand the mechanisms behind them. I don't drink pond water even though I am neither a microbiologist nor a public health expert. I wash veggies before I eat them, and I wash my hands before I eat. I take medications exactly as my doctor tells me to and I consult with them before changing things.

You may be thinking at this point, "but I understand all of those rules, why should I follow rules I don't understand?". Fair question. For children especially, but also for humans in general, I think the knowing of a rule has to come before the understanding of the rule. Understanding is where nuance comes in. You know the saying "there's an exception to every rule"? There are some people who take this to mean that rules can be shrugged off when inconvenient. These people are, largely, fools. The exceptions to rules can only really be identified when the rule and it's motivation are clearly understood. Sometimes when I'm doing emergency repairs on a software system, I will ignore the usual rules about code merges in prod. This has backfired on me before, because I did not take the proper alternative precautions one should take when moving quickly, but most of the time I think my handling of exceptional cases has been pretty good, because I have a good understanding of why those rules exist, the problems they're supposed to prevent, and when they can be safely(ish) broken.

Which brings me to my final point about wisdom, or understanding. Knowing about a rule, or fact, or domain of knowledge can feel an awful lot like understanding. Most humans suffer under this delusion, in most areas of their lives, for the full duration of their lives. Understanding usually only comes when one is confronted with an undeniable refutation of what one thinks they know. And that always takes time. In most cases, on most subjects, it never happens and we go to our graves never knowing the full extent of our lack of wisdom. Usually the best we can do is sort of grasp around the edges of our towering ignorance and try to get a feel for where the contours are, and the better we can do that, the better we can at least guess about what we don't understand, and I think that's the closest to wisdom we can hope for.

screen time is just a limit on time to learn if the kid is using it for the right purposes which you should teach them to

Part of that is teaching them moderation. Spending 12 hours a day on a screen, even if "learning", is not healthy.

To set the stage, I HATE when people complain about younger generations, because EVERY generation did the equivalent at their age.

Young adults that just finished school, whether that includes college or not, have had a very limited perception of the world. It's not their fault, they've only lived "the tutorial of life" up until that point. Having a job, paying bills, getting married, having kids, watching loved ones die, and all the other experiences that don't occur until later give you me perspectives and lessons.

I've met some wise kids that have lived through things that I have yet to experience, but it's a pretty safe bet that an 18 year old is probably not the best person to give parenting advice. They could absolutely help give additional perspective, or share ideas you hadn't thought of, but as far as real world experience, they just don't have it yet.

At 18 you are still stupid but at least you are legally adult. That is it.

I remember me when I was a teenager: I was a dumbass.

Everybody I knew from school? Also some sort of dumbass.

I was slightly less of a dumbass at 18, but still definitely a dumbass. I think that number just gets settled on because it's the legal age where you are considered an adult (though by actual biological standards, your brain doesn't even finish developing until 7 years later).

Is it stupid? You bet!

That's probably the main reason for it though. More likely than not, you'll look back at your teenage years 20-30 years later (or sooner) and realize how foolish you were. Wisdom usually comes with age (though not always).

I suspect the very small number of people I have blocked on the Fediverse are minors or very young adults. You can tell.

screen time is just a limit on time to learn if the kid is using it for the right purposes which you should teach them to

Even if all you were using your screen time to do is learn, it is still unhealthy.

At a certain point, the ability to affect change or implement what you want on a large scale requires being a leader of others. It turns out that leadership is a skill best learned through practice. A lot of leadership skills come from interpersonal skills which also come from practice relating with others.

You don't learn these skills staring at a screen or a book, but interacting with people.

Kids may have knowledge but wisdom how to use it often comes when personal responsibility kicks in.

Like I do know how to do shenanigans. I've had that knowledge since I was kid. Now I won't do it as I'm acoountable for my actions and I can refer to what other people feel about them. So it's wise not to.