> I think the point was that they were declarative ...

> I'm deeply familiar with React

I'm not trying to be snarky here but... React is not declarative.

Though it's good you highlighted that as that is essentially the fundamental difference here: WPF/QT are declarative, CSS is declarative, UIKit is (mostly?) declarative, HTML is declarative(-ish). React components aren't.

I have to disagree. You produce a data structure representing the UI. That's basically the definition of declarative. Just because you can build that dynamically doesn't mean it is not declarative. You could always build up XML dynamically as well.

It's a far cry from an immediate mode API where you are making draw calls.

A React component is a class or function - there is no static "data structure", except for what any individual dev might define as convention for their own application. Unless we're calling class members "declarative data structure", in which case we may need to revisit some definitions across the programming world.

And it's not really representing UI: that's the main point here. Layout is decoupled; it's only really representing front-end logic and state.