That’s just total nonsense. React is a tool like any other, and it can be used to build simple UIs or overwrought complex ones.
My team have just reimplemented a UI in React that was previously built using static pages progressively enhanced using JS. And you know what? It’s faster, easier to use, more accessible, looks better, and well-tested (though unfortunately I can’t show it off, because it’s a commercial product).
I would guess you are just conflating bad UI decisions like Reddit’s with the fact that React is now popular for building UIs.