In my opinion crypto will never be able to replace fiat, this is because crypto is decentralized so that it cannot be used globally for direct transactions such as fiat, of course it is difficult and confusing for retail sellers when prices rise or fall by 10% per day.
I think otherwise, because crypto is decentralized, it is able to pay for almost all goods globally if it is agreed on a payment instrument. Crypto currently has a very volatile value and it is difficult to provide a stable value because there are many price settings by whale and certain parties who use the open market for crypto