The reactivity system in react is certainly "outdated" when compared to Vue, Svelte, Solid, or pretty much any newer framework. But it's just as you said, the larger ecosystem does have its benefits. There are a few libraries like Framer motion, that don't have equivalent support in other frameworks.
Before React two-way-binding of data, known today as Signals, was the way we did things. Angular is probably the best example from the pre-react time of that.
React came along with a philosophy of one-way-binding also known as unidirectional data flow. I’ve stuck with it because I think it enables much better local reasoning, and more predictable outcomes.
Neither are outdated.
I’d wager the most performance critical use cases would benefit from signals, things like tldraw.
But unless you’re doing something which needs to paint every single frame (ignoring animation/transitions), the extra overhead and mental load required by Signals is excessive. It’s overly complex and harder to reason about.
With no disrespect to Vue, Svelte, Solid, etc, they feel outdated in the way Angular does.
