I don't understand your point. No one is disagreeing about the contribution that big finance has made in shaping our current systems. FB raised money, got listed. There's tons of financial system which helped them and help everyone from invoices to making a trip everyday.
But that doesn't mean something better can't come up. People don't hate banks for the monolith but their monopoly like nature that had stifled innovation and displayed outright criminal behavior. Don't forget 2008 recession was triggered by banks. Recent libor scandal..
About the technology investments. I would argue against this. Banks are more regulatory and defend my turf play than a technology play. Have you ever worked for a bank or any finance facing institution. There's layers and layers of clutter. Whole party is one big monolith, sucking money from places that it doesn't deserve.
Biggest benefit banks provide as in traditional banks is the account and trust that, that money in the account will remain on the name of holder. That trust as well was breached multiple times during withdrawal limits and freezes.
We all need better alternative. May be FB won't be the one. May be bank themselves will become more open and lean. But someone needs to push. There's a lots of money to be made and quite frankly FB deserves it for trying.