It enables much of what a large framework like React enables, but with a much simpler implementation, less tooling need to use it, and (some may argue) more convenient usage.

Understood, but is it worth another learning curve?

I'd say if you know React or Vue or another framework and it fits your project well, then no. If you are learning though, there is arguably much less to learn (in particular, not having to juggle 3 languages). And if you are building something very serious, it's suitable: nearly all of Grist frontend is GrainJS, and it's a very big performant real-time collaborative long-lived single-page app.