If you're looking at purely static websites, then it's just a way to structure your application; matter of taste, I reckon, and there's plenty of alternatives on the market that go back twenty years if need be. That said, personally I'm quite fond of the component based approach to building websites - and React isn't the only player there.

But the strengths show when you combine it with e.g. Gatsby which turns it into a hybrid website + app. For first time visitors, search engines, and people with JS disabled it's just static HTML, simple. But for most visitors (browsers, JS enabled etc), after the first load it turns into a webapp and any pageview only requires a single .json file to be pulled in, which can be prefetched (on link hover for example) as well. This gives it the performance characteristics of a single-page app.