You are quite right Bitcoin possibly cannot replace Fiat. The best possible outcome is Bitcoin will only become more adopted as a currency for transactions. However looking at the odds this is still going to be challenging based on the fact that most governmental laws are against Bitcoin in many countries and also because as Bitcoin adoption increases so will fees.
Bitcoin wasn’t even invented by Satoshi to replace fiat currency but rather to be an alternative to it. And if you ask me I will say it has actually play that role perfectly for someone like me, i use it mostly for only cross boarder transactions which if I am to go through banks will actually cost me a lot and will be a thing of stress.
I don’t agree with the bolded part above as I believe it is probably a typo from you. I don’t see bitcoin been used as a currency for transactions due to the recent high transaction fees most especially for small scale transactions rather an asset for investment because of its ability to hedge against inflation making it a store of value.
However, you should not be pessimistic because I believe that there are millions of those who own Bitcoin and they will not give up so easily, and if we have ever been at an advantage, it is today, because we understood what Bitcoin is much before them and we have much more of it than them. If they want it, I tell them "the price is $10 million per BTC" and only if you ask me nicely
I am among those who are still optimistic about this transaction fee of a thing, I believe the said bug which the ordinal developers are exploiting will soon be addressed by bugs. But for now, i am treating it as an asset now and only make transaction with it only if fiat currency will be an hassle for me