"It's the same for the creators, though - they can't move off of YouTube entirely, because none of their viewers will go to a PeerTube instance just to watch that one creator."

Is it so hard to be on both? Something I like about YouTube compared to some other platforms is they never (to the best of my knowledge) engage in exclusives or impose exclusivity conditions. And even when they develop new features, I've rarely seen Google try to restrict those.