You can buzzword all day long, but that doesn't make the typical React component any more declarative than the next script. Components reyling on internal state, querying that state and then munging some JS code into some HTML-like template and mutating the state again, when a user interaction happens -- That's hardly a declarative UI. It also does not become more declarative due to using an angle bracket notation for components.

One can look at some Prolog code to get an actual idea about what declarative means. In React you are not writing down constraints and logic rules, according to which React automatically figures things out. You are not working with relations, which need to be kept true. React is far from a configuration only kind of framework.

To claim something like one cannot be productive without using React or similar framework is really a silly thing to claim. Most websites do not even need to use any such framework, because in their nature, they are not interactive. They show information and that is it. Then there is a set of websites, which has here and there some small interactive widget, which one could argue to use a framework for, in parts, not for the whole friggin website. This still allows for people, who merely want to retrieve the information and leave without interacting. The third and smallest category is then the set of websites, which actually need interactivity and state in the frontend everywhere, where such a framework can be justified.