I think it could be argued to have been, at times, conceptually thin, if you like.

I agree that the tooling and even React itself, under the hood, have never been thin, or if they ever were it was only very early on in the project. Well-functioning enough that one could forget about them at times, maybe, but not thin.

Oh no, JSX that compiles down to the exact set of `new Object` calls you would expect in a tree structure, how can I understand such complexity!?

Really, you're kidding yourself if you think React isn't far simpler than Angular or Vue or any of these other frameworks. If you have some different direction in mind, fine, but I doubt it scales

Don't misunderstand. I like JSX. However, that doesn't compel me to call it thin.

I find that strange. For example, I would call Angular or Vue "thick" with their extra templating files and DSLs and two-way binding.

I would call React thin because the JSX components you build are transparently just objects, they interact with types super gracefully because components are just classes with a method that returns nested objects, and your code is just invoking JS and producing JS until the React library itself performs the side effect of rendering.

I understand that React has abstractions and a heavy scheduling engine and all sorts of complexity, but a React component - the core concept of React - reuses directly JS concepts in place of introducing its own in most situations. That is thin.

I admit that if you are just thinking of libraries in general, of course a frontend framework is not "thin", but for a library which enables true composability and reuse, React is so thin compared to is competitors. Which seems a reasonable de facto context for a conversation about React.

I don't think it's thin even in that context. For example, invoking a hook comes with a bunch of rules beyond "just javascript". You shouldn't invoke a hook conditionally. You shouldn't invoke a hook in a loop.

I've run into state/props mismatches due to the diff resolving differently than I thought it should. It's possible to solve this, but it further breaks the illusion of a thin layer.

Maybe it's a different way of thinking, but I don't think two-way binding is inherently thicker. To me, thickness is related to the amount of "mechanism". A handlebars-type templating system seems much thinner to me.