Currency isn’t meant to have intrinsic value because it’s meant to help transfer value across the system. If a currency is worth investing in, then it’s not a very good currency because it’s not meant to have intrinsic utility beyond its ability to represent value.

It’s supposed to encourage people to invest their money in things that have value in themselves and to keep the currency flowing. It punishes rich people far more than poor people because poor people spend their money basically immediately while rich people keep most of their money. If you want to critique the class divide then go after employers who don’t keep their wages tracked to inflation, and those who refuse to pay their employees a living wage.

There’s lots of ways to critique economic policy but “it’s not backed by anything” is a poor argument because that’s the entire point of currency. You can argue about how price for value of work and products is an inherently irrational concept, but currency not being backed by any physical object makes logical sense if you agree that price can represent value.