I admit I worded my comment vaguely because I was rather tired and wasn’t sure how I should express the nuance I feel around that. But to fix that:

In my experience, going from a reasonable, mutually healthy level of intimacy to one party just completely lacking interest is essentially never the core issue in play, but it is an exacerbating issue. For instance, with my ex, who I was with for five years: for the first couple years, things were pretty great. Then she ended up slipping into perhaps the worst long-term episode of severe depression and video game addiction I have ever seen in my life. I’m talking 12-14h at least a day in a KRPG, completely withdrawing from IRL social interaction (including with me, for the most part) and supplanting it with constantly being on voice chat with the various clans she was a part of over time in the game. Mind you, I enjoy gaming myself, and have struggled with overdoing in the past as well, but never to this extent in terms of length and severity. And despite trying to find numerous ways to help/support her, encouraging her to find different and better therapists and psychiatrists, and figuring out how to rebalance her meds - including offering to just be on the phone with me for 30 seconds at the beginning of the call and just saying “I give permission for my partner to discuss this stuff with you and try to find a better solution because my mental state prohibits me from doing that right now”, being effectively unable to make any motion in a positive mental health direction. To the point that it got so bad that I became severely depressed and began aggressively self medicating, eventually to the point that I realized staying in the dynamic would probably kill me, in a very literal sense. She would barely come out of her room for dinner towards the end, and I was absolutely not about to get her to just let me “use” her for intimate gratification when the chemistry was completely gone and she was gonna just lie there like a fish - I’d have felt like I was assaulting her, and I refuse to do that.

So: no, it shouldn’t be the grounds for a divorce (or partner separation, I happen to not give a shit about marriage outside of the context of tax benefits, but I take a committed partnership very seriously), but it can and should be considered an exacerbating circumstance in a relationship that has extremely serious, long-lasting problems that essentially put everything into a death spiral.

Also: I’m sharing this for context and nuance as an explanation of my opinion. I’m not asking for or desiring feedback or constructive (or otherwise) criticism or judgement. Me explaining this is an infinitesimal fraction of the lived experience of it, like you saying your partner is “pretty cool”, when there are myriad shades of nuance to a partnership. It is a closed chapter of my life, and I am better for it.

In what universe do you live in? Because in this one, it's not the men who are being beaten, abused and raped in their own home by their own partner, is it? Look up surveys and studies, if you find this in any way surprising.

I fail to see your problem with "withholding intimacy". Nobody is forced to consent to anything, and if someone no longer wants to have sex with you, then that relationship has very serious problems.

Lack of sex is a symptom, not the cause, and if you think it's being used to "punish you", then you need to take a step back and have a very long think about what is going on from your partner's perspective. If you're unable to do that, then find help - a therapist, a psychologist, a councillor, someone that is unbiased and that can help provide insights.

Ultimately, you may come to the realisation that your partner and you have needs that the other is not willing or able to meet, and that it's time to go separate ways. Or you may both come out of it with a better understanding of each other, and live happier lives because of it.

But let me tell you, the fact that you assume that you're being punished because you're not getting sex, that's one massive red flag.

NO. It is, quite literally, the opposite. How do you misinterpreted it that badly?

A marriage is a legal contract, and it binds the parties to mutual support, fidelity, respect, and cohabitation.

This serves to clarify that sex is NOT included in that list of obligations, but do note that fidelity IS. You don't get to get to justify cheating with "I wasn't getting any...".

That said, the parties are obviously free to come to an agreement on what works best for them - and if that includes extramarital sex, then that's fine as long as both agree.

Your argument seems more against religion (and inferrably monogamy) than it does marriage itself. Especially if "civil union" is your alternative.

I don't see what the benefit would be to just go through the family law and replace the term "marriage" with "civil union".