a 51% attack has a small chance to undo a spend that was done just in last hour

It can alter or reverse transfers as long as it's going on.

IOUs based on a “trust me bro its still there asset” is not as good as IOU based on bitcoin

That would be better actually, because there might be a real thing somewhere which the writer of the IOU will give the bearer upon demand. Bitcoin is "Thanks for the $97,430.23 bro trust me bro someone will give you that much or more for that ledger entry in money, goods, or services bro I swear bro because it's scarce bro".

The argument that you need to convince bakers in your new country to accept bitcoin is not real. But its easier than gold, tulips, or other currency, or land deed in civil war country. Replace baker with someone on craigslist, and its still easier.

Yeah, today it is easier, because it's bolstered by drug dealers, nerds, and speculators who do their day-to-day living mostly in USD. But in 30 years? I'm not psychic, but I'm guessing that drug dealers will switch to more privacy-focused systems, (tech) nerds will switch to more technologically interesting systems, speculators will find other things to speculate on, and the...right-libertarian nerds might keep the network humming along at a much lower valuation if they don't all collapse in existential horror at the price drop.

You’re arguing here that paying with Bitcoin is bad for the payer because value is certain to go up.

"Certain" is an overstatement, but yeah, you can't really use a deflationary money, because it makes more sense to hold it. Money, as a medium of exchange, needs to be stable, erring on the side of inflation. Bitcoin is bad at being money.

That means it’s good for the buyer/receiver, which makes it easier if you need something physical/consumable from your “wealth”.

That's the theory, but aside from being no way to create an economy, it doesn't follow IRL does it? People aren't exactly clamoring for my Bitcoin. My inflationary dollars are far more in demand.

Bank panics/failures are ~~frequent~~ serious enough that the system relies on bailouts for them. And yet the system works. Neither I nor my parents have ever lost money from a bank failure. Despite some of our banks having failed. Meanwhile the Bitcoin I bought when I started typing this is now.....$96,990.40. I've lost a month's groceries doing nothing.

USD has no relevance to value of bitcoin.

And yet even the ASICs I can buy with Bitcoin, like the beer I once bought with Bitcoin, all describe their prices foremost in USD. Because that's mostly what it's actually bought with, and sold for.

You know, blockchains are neat and by virtue of that Bitcoin is neat. But there's nothing particularly good about it, and it's rife with flaws. Its principles are flawed, and it's not backed up by anything but hopes and dreams. It's a fun thing to gamble with, but there are more interesting blockchains, and no blockchains are mature enough to be really anything more than just fun to mess with.