I'd tend to agree with the parent here. Then appeal of React is that it's one piece where everyone else is trying to develop a full stack. Your needs for that single piece will be more consistent across projects that are either legacy or new.

A full frontend stack is total overkill for the vast majority of projects that fall under the "open, check, close" use case. So many of the perks of those frontend stacks, such as keeping data in the browser and only reloading certain parts are based on the slow load times of a full frontend stack if you don't do all of those things.

Being able to use pure React both client and server side without anything else is a fairly significant perk.