National currencies ARE fiat currencies.

Not always, the USD was on the gold standard 100 years ago. These days, most (all?) are fiat, but I separate the idea of fiat from national currency because they’re technically separate concepts. You can be against fiat but not against national currencies or vice versa.

The value of money is all made up

It’s really not, it’s a very complex system and would remain complex regardless of what monetary system we use. Fiat currencies, for example, are managed by central banks to maintain a predictable amount of inflation, but that’s going to be an average, and different sectors of the economy inflate at different rates (e.g. housing has been inflating faster than food recently).

Even if we completely eliminate the concept of money (not happening), the complexities of large scale distribution of resources would still remain.

That said, modern fiat currencies do a pretty good job of distilling that complexity down to a common form of exchange. You work for some amount of money, you exchange that money for some goods, and the person providing those goods exchanges it for yet more goods. That prices tend to stay reasonably stable the vast majority of the time is honestly pretty amazing IMO. And people starving or freezing to death is incredibly rare in most parts of the world, especially when the fiat systems are largely kept out of the hands of politicians.

My personal preference is more competition in the currency space, so I want to see actual uses of cryptocurrencies, fiat currencies, and even gold-back currencies. In today’s age, it’s pretty easy to manage that complexity, and having some competition should keep each of those currencies honest, because people can always vote with their feet and their wallet.