I think understanding the proof of work concept and embracing bitcoin-only are one and the same thing. It's the trickiest part to understand and also the one that binds the whole thing together to make it real money. I was re watching this vid the other day as I wanted to share with some friends, and there is this very telling phrase at min 5:22 "If you don't have human effort on both sides of the equation, you don't have a real equation, it's a social equation" and they show some images with gold miners. Bitcoin is money for the same reason that gold could be used as money for several thousand years. That's the basic difference with fiat and the proof of stake, it's just a social convention and as such can be changed at will and not anchored to reality, physical reality. I also remember one day a tweet, maybe by @dergigi where it said "bitcoin is not backed by anything, bitcoin is the thing" and it was an aha moment where I understood that money cannot just be an abstraction or a convention between participants, it has to be something that cannot be changed by opinions or majorities.