The problem is that the purchasing power of gold isn't relatively constant: what you can buy with 1 oz. today and what you can buy with 1 oz. tomorrow are not necessarily the same — so you have much the same problem.

Moreover, the relative constancy of the gold supply is a problem, because as the economy grows that makes each unit of gold more valuable … which leads to deflation, which is far worse than inflation, and can lead to utter economic desolation.

I hate fiat money, I really do: I hate that governments can inflate their way out of debts and inflate away my savings. But gold — appealing as it is — is even worse.

1 oz. of gold doesn't change from day to day, rather, only people's opinion of it changes. In that sense, is there anything you can think of that people would want as much or more in the future than they do today? I can think of maybe 1 thing, sex, but I don't even want to begin to imagine how a system like that would work haha.

Ultimately I agree that fiat currency is a necessary evil because of the ability to expand with the economy.

Gold is essentially the same plus liquidity trap (think of Bitcoin and it's deflationary nature)