Compared to the seemingly arbitrarily split js files filled with jQuery at other large projects I've worked on, I'd take a declaratively described component per-file React app any day.

I remember trying to find the class for the element I'm manipulating imperatively in jQuery in an equally arbitrary CSS file only to realize almost none of those attributes are applied cause some other more specific selector in another file took precedence. That's obviously due to poor organization, but at least React is readable with HTML, JS, and CSS all right next to each other with very clear intent due to the declarative style.