You're basically saying that crypto has failed and would never be able to govern its own communities. This is a fair assessment to make until physical crypto communities start popping up in the real world and governing themselves.
It's also unclear if by "fiat" you mean "debt".
Governments don't have to exist in their current form but debt might.
Of course if everyone is rich the need for debt becomes increasingly lessened.
I think I maybe didn't convey what I was saying well. I believe cash will eventually play the physical representation against Bitcoin standard in the future and Countries will base their printing off crypto holdings rather than debt! Cash to have it's value against crypto like bitcoin so to speak. At least I hope that is how crypto will defeat money printing or debt aspect of fiat.
So that is correct, I am not talking about the gov controlled debt/printing aspect of fiat as we see today. Just a physical medium that some or many will continue to opt for and I think cash still can play a roll in that in a crypto standard world as the physical medium. I doubt we will ever see the day where people are holding physical satoshi, at least not in the immediate or near future, but I do expect countries will continue with autonomous use of cash in their given localities and that is the shift we look for next. :)