While [lots of divs, inline styles, focus management problems] are valid concerns, it should be noted that nothing in React prevents us from building accessible web apps.
True. I'm quite capable (and sadly, guilty) of building inaccessible interfaces with React or without.
I'm optimistic though. For example, React has a blessed tabs solution that is accessible out of the box. I reach for those, and thus my muscle memory for building tabs now results in a more accessible product. And when I need to do routing/linking with React, I reach (get it?!) for Reach Router, and I get accessibility "baked in," as they say. That's a powerful thing to get "for free," again, as they say.