[shams93]

Back when browsers were wildly incompatible jquery was a life saver. Sure you could do painful dom code and then have all kinds of libraries that have to be loaded in the right order to support all browsers or you could just include jquery. Now in the era of the progressive web app SPA jquery is outdated. Even for low level dom its still outdated because modern browsers follow standards really tightly especially compared to the bad old days. Frameworks are starting to get outdated in the face of tools like Svelte as well as Polymer 3. You can pull off a SPA with Polymer 3 on modern browsers with no shims at this point, except maybe shadow dom, but Polymer 3 has selective shimming so you don't have to download one huge shim file.

[Vinnl]

jQuery also predates standards such as querySelectorAll and fetch, so no, it wasn't just compensating for browser incompatibilities; it also provided a far more pleasant API.

React is in a similar boat - it provides a far more pleasant experience keeping the DOM in sync with your application state, in a way that Web Components don't (although they have other advantages that make them great when used together with React).