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.
I agree with learning React, it pops up in all sorts of places, vscode extensions, the windows start menu apparently.
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.
You can still write class-based components in React, no problem. It might not be in vogue, but for the most part, you can still write React 18.x roughly the same way you wrote React 0.x.
