Have you actually made a transaction on chain lately with Bitcoin? Do tell us the experience of grabbing my popcorn and waiting for it!
As for Bitcoin replacing banks, banks offer loans, how could Bitcoin offer you loan when you don't have a penny?
I recall about the transaction fees, but there are already banks which loan bitcoin called exchanges. I know that there is much less volume on exchanges, but at least it shows some people borrow in bitcoin.
Bitcoin is more like a replacement to saving in gold to me, rather than a replacement to banks.