Gold does not have to be backed by a commodity, because it is a commodity.
I don't agree that it's useless.
I don't agree that perception is reality. Reality is what is is. regardless of what people believe it is.
Adams Smiths greatest student, J. B. Say, wrote two centuries ago: money is indebted for its currency . . . to its being a commodity bearing a peculiar and intrinsic value.
"I then submit to you that Bitcoin is a commodity as well." As written by me, the greatest me there will ever be.
And well surely you agree that many other metals are much more useful than gold though, why aren't they more valuable?
Then the reality of the matter is any of the money you have in your wallet is just paper, regardless of what you or anyone else believes it to be worth. The idea of worth and value is defined purely by perception, the only other option being perhaps God.