You learn vanilla HTML/CSS/JS (I think Mozilla has good courses on those). After making a few websites that way, you learn Svelte and you live happily ever after.
Avoid React, NextJS at all cost especially since many of these new frameworks actively try to screw over new developers with PaaS.
I think React peaked with hooks around 2019. I write most of my front-end with the smallest 'React-like' library possible (Preact) using only functional components, and with as little 'magic' from useEffect etc. as possible.
I like to stay close to 'raw' HTML/CSS/JS when possible, but the web platform APIs are just a little to clunky and verbose for me without the JSX abstraction.
So new projects have to actively not follow the recommended approach in the docs if they want to use vanilla React.
But otherwise, Svelte has a very low surface, everything else is just standard vanilla JS/Html, also one thing that Svelte has over other frameworks is that vanilla JS libraries just work, no need for a wrapper any.