I agree that cryptocurrencies and superstitious fiat currencies have their own niches for use, where each of them has competitive advantages. It is also impossible to consider all cryptocurrencies as having a single function. So bitcoin and ether are not very suitable for micropayments, but for example, Tron or CHIA, on the contrary.
Bitcoin is still suitable for small payments, there's the lightning network and even if you use bitcoin, the fees are not that really high this time.
That's why El Salvador has adopted it as a legal tender and they're seeing the good side of it not just as a payment but as well as a store of value.
I've always thought that the biggest thing bitcoin/ethereum is doing is being an alternative payment in every country, but it won't be able to replace Fiat. however, when El Salvador accepted bitcoin as a legal tender, I thought that the potential of bitcoin today could replace Fiat.
although at this time bitcoin is still quite difficult to replace Fiat due to various regulations, but I think the development of bitcoin to become a legal payment alternative in a country, is an extraordinary thing.