A LOT of websites don't need a "front end" framework (apart of the one that is already there: html, css).

Could need some js library and that is a maybe.

In general:

If is like a eCommerce site, blog, wikipedia, forum? Not need

If is like a Game, Paint app, form builder? Need.

And how you learn it? Not use a framework, and try to stay with things more minimal, like tailwindcss.