For me, i do not think bitcoin can replace fiat totally, because when their are larger transactions to be processed, it takes hours or even a day, except you have to pay Higher fees to process your transaction.
I will love several suggestions below, to further enlighten and brighten my knowledge.
We are of the same mind. I like bitcoin, but I'm not interested in using it as a payment tool, it's not effective because the volatility is very high. It could be that you buy a cup of coffee for 0.005Btc, and a few months later at the pump, with the same nominal you can get dozens of cups of coffee. With these facts, BTC is more effectively used as an investment tool. and other technical matters related to the duration of the transaction, fees, etc. as you mentioned also reduce its effectiveness. But it is undeniable that someday it can get better and this shortcoming can be eliminated, but for now fiat is more effective as an instant and small scale payment.