What we call today 'FIAT' is just a piece of paper without any ballast, money needs to be a scarce resource, like precious metals, for example.
However, precious metals like gold can not be used on a day to day basis, so they are restricted to the value reserve. Cryptocurrencies on the other hand are easily divisible, allowing their use as a means of payment in our daily lives.
Modern economic theory says that the Fed can print as much money as they want as long as it does not generate inflation.
They keep tabs on inflation. If inflation is low then they can print more money.
That's where the problems begin: only big banks have access to this cheap Fed money. Basically they print money for themselves and everyone around the globe works all their lives to keep inflation low. We work for the Fed and their partner banks.
Since they keep printing trillions in debt, we have to work more and more, exponentially, to keep the pyramid system going.
I don't know how such a system is accepted by everyone. Basically you have a couple dozen banks around the world accumulating most the existing wealth.
2008 exposed all this when banks were bailed out. Lemonade stands don't get bailed out, mom and pop shops don't get bailed out. Banks do.
I see Bitcoin as the new ballast. Impossible to print more Bitcoins for your banking buddies, impossible to do anything shady because it's all public.