It seems to distinguish between frameworks and dedicated libraries, so I think we can apply a react test here: Is react a framework?
Very clever!
In reality, you'll most likely be a software engineer specialised in react development.
Frameworks catalyse development. It's much easier for a new team member to read the very rich and well explained Django documentation than to pour through reams of poorly documented code for a custom mvc for instance.
This feels like both tilting at windmills and irrational expectations on devs who for the vast majority need to turn out features, not core libraries.
... the declarative pattern is a part of React’s way.
Where there is a “framework’s way” of doing things, there is a framework.
In software it's the same thing. The framework defines the structure, you just fill in the blanks like you would fit floors, add wheels, etc.
The pro is that it's an easy way if you want to build an application that closely follows an existing type of application. But it's too constraining if you want to be able to customize the structure down the line; all of a sudden, you realize that it's defined outside, in a technology that is not your own and you don't understand.
React is a library because you can have websites with as many render roots as you want. You can use it only for small parts of the site/app, control all of the props from the outside, etc.
People use it as a framework because they take the SPA route with a single root. Usually a bundler even generates the HTML file for them, tying the entire app to a single render call.