That's true. But it is also true that, in the specific case of the US dollar, it's backed by US hegemony. That hegemony is brittle, and supported by an outsize military that was misused in a way that almost broke the nation in combination with a derivatives crash that could easily have caused a global depression. The US's ability to get away with ZIRP, QE(n), etc. rests on "You and what army?" and on a hegemony where vassal states have no decision-making autonomy and submit themselves to US surveillance.

We're only partway out of that crisis, and it could come roaring back. Chest-thumping about "Where else ya gonna go?" is unproductive.

I don't see US hegemony as good or evil, except if you call brittleness that could lead to a very deep unprecedented crisis "evil."