React's been around long enough and is dug in deep enough to have decent ROI on knowing fairly well, but the recent obsession with Next.js and SSR...maybe not. Privately I think this might be their undoing.
But yes, mixed-rendering, server functions, meta-frameworks, etc. You are in real danger of spending years learning all this stuff and still not being any closer to knowing how computers work.
Hooks or classes?
Or whatever comes next.