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 agree with you because people still using fiat than crypto and they prefer to use fiat to buy something. but this will change if all people know crypto and they know how to use crypto and they like crypto so crypto can replace fiat. maybe this will happen in the future as we see that the technology still in the development and everything is possible to happen.