And if you don't buy it, you can always earn it in other ways. One mainstream way is by mining them.
So even if the bridge between crypto and fiat is somehow cut off entirely, crypto will still keep on living.
Don't forget you can also sell your services for BTC (and other cryptocurrencies, of course). Anyone can send you coins directly on the Blockchain (P2P) in exchange for a good or service. You'll save big on middlemen fees (from centralized exchanges, banks, etc) this way. The only downside would be market price volatility. Your coins could lose value in the short term if market prices go down all of a sudden. So the risk of loss will always be there.
You're right that crypto will still keep on living in the aftermath of a Fiat on/off ramp collapse. That's because crypto was designed with decentralization in mind. Nothing can stop the revolution. I'm hoping the UX (user experience) part of crypto improves to a point where sending/receiving money becomes as easy as sending an email. With ease of use, people will find crypto (especially Bitcoin) a more attractive option for digital payments. Who knows what will happen in the future?
