So easy in fact that even the company that makes React can’t use it in a way that makes their site fast.

That doesn't say much about React, though. Indeed, you can open the network panel and watch requests go by over the seconds that it takes to open, suggesting that the issue likely resides on the backend.

So the company that invented it does not know how to properly use it?

Or are you implying that React does not fit FB use case?

He's literally saying the front end technology doesn't matter at all in this.

Are you just going to defend React to the bitter end? Or do you just enjoy imaginary binary choices?

I think I was not clear in my question:

I don't defend React. My question was almost the opposite and I was trying to ask:

So if even Facebook has a problem with using React then who has a better examplea about why and how to use it?

but i think the reason for +1s, +2s feeling comes not from the client side aka react, render is fast, but they do make two requests to backend which takes ~230ms (for me in EU) and one request of ~130ms every other click on already visited chat/group chat.