YMMV. I've been involved in multiple large-scale React projects at this point, and they
all eventually suffered from performance issues, related to React's rendering model. And fixing it is always painful.
On Reddit, as another comment mentioned, yes, React seems to have been a major factor in how slow it became due to the patterns it encourages, and the massive JS sources.
You can only 'get very far' because browsers are crazy fast and you don't notice what's going on underneath. Until it catches up to you.