Personally, I just find Elon's tweets entertaining but from a crypto market investing point of view, I don't pay much attention to them. The whole Bitcoin fiasco kind of shows that maybe he doesn't have the best interests of crypto at heart when he talks about these sort of things.
Anyway, all I can say is that fiat is definitely not the solution as we reset the financial markets. Reserve currencies are never forever. We've seen them switch from the Dutch guilder to the British pound to the US dollar over the course of centuries. Gold has remained a constant in the background. Time we added Bitcoin to that.