However, the number of websites where a full-blown library like React is the right tech stack is probably less than 5%. For everyone else you would want to use vanilla JS, though if you are already familiar with jQuery I don't think there is anything wrong with using it.
The funny thing is I spent years using jQuery and have also used Vue.js, but I'm just so tired have having to deal with importing libraries, setting up build systems, etc. that 9 times out of 10 I will just use vanilla HTML/CSS/JS and call it a day. It is just so much simpler. YMMV
For a normal/small website, there is no need for a framework like that which adds unneeded complexity.
The developer ergonomics, and the mental models which it prescribes - which are why I’d argue it’s actually a framework and not just a library, but that’s semantics - are really well thought out and can make you very productive.
If I want to build a static site with minimal fuss I might still use something like HTML, Sass and vanilla JS with Parcel. For pretty much everything else React has become a default.
Throwing together an API in .NET Core and a website consuming that API in React takes less than 5 minutes to get going.
Think making use of html `canvas`. Though there are nice libraries that abstract the ugliness like react-canvas, it would lead to less reusable code than the jQuery equivalent, imo.
There's one use case that might remain: the jquery plugins ecosystem. You can find many replacements on npm, but they're a bit less beginner-friendly.