With such a crazy high transaction fee and delay confirmation time....Considering BTC as FIAT is just a nightmare. Lets understand it one example...after buying essentials from a local grocery store worth $10000 and want to pay through BTC but this transaction will cost me $200-250 which is crazy. So using BTC as FIAt now is not practically feasible at this point of time.
So, you are right, using as FIAT is something that just cannot work out at least for now until when we see the scaling solution solved and then see how things would end up as.