> That is the "rehydration", taking a React app that you wrote and the server buildchain "dehydrated" (baked into HTML + CSS), but then rehydrating it to add interactivity back. Yes, you could do all that manually, but Next.js makes it magically trivial... you never have to think about it, it just works. And it's lightning fast.

Actually I think the big trend in JS front-end development is realizing that you do have to think about it! React rehydration is often a very slow step (whether it's Next.js or anything else, I don't think it makes a difference), definitely not "lightning fast" on non-trivial apps with lots of data. Islands architecture goes a long way towards solving that but it's still a bit limited today.