The systems I work on at work use a Java based back end and we're not going to complicate our back end more by adding a node.js sever so we can SSR, I know a lot of those hooks have to do with that. I have a bunch of demos that do graphics-heavy stuff with three.js, AFrame and such and if I publish these to the web one big advantage is I can upload them to S3 and publish them to a CDN and be done except for paying the bills, so again, no SSR. [1]
It's not so clear to me if useTransition, useOptimistic are part of the problem or part of the solution. (e.g. "looking responsive" could be the enemy of "being responsive", right now I am fixing a ticket about an incorrect state that flashes for < 0.5 sec that drives some people crazy, if I wanted something different in my framework it would be "update the UI state once, it renders once and doesn't keep calling effects and setters for an indefinite time")
Funny I am advocating for a React 19 update because at least React 19 can tell the test framework when it is done running callbacks, it might have me writing tests for components again.
[1] ... and if I want to SSR I might just ditch React and build the kind of apps that I built in 1999 with maybe a little help from HTMX