It's certainly easier to just include JQ on an existing site and get to work for simple stuff, but I just deal with Angular now. Easy enough to get up and running with ngcli, and a year down the road the codebase won't look like the abortion which is loads of jquery.

To a certain extent I have left it behind as well, but jQuery does add an extra level of convenience that is well suited to prototyping (and even getting things done quickly in prod). One example is the each function that works on object properties. Getting that to work on an older browser without jQuery is a bit convoluted, but with jQuery it's easy. Not saying it's the only/best way to do it, but it is probably the easiest.

It's definitely less necessary than it was a few years ago.

I find it useful when you just want to add a little bit of interactivity to a mostly static page, and you're not sure who's going to be maintaining the page in the future or trying to use it as a template.

A lot of people who know a decent amount of HTML and CSS but aren't that familiar with straight JS dom manipulation, or what functionality works cross-browser, can tweak jQuery-based code more easily. That's really a tribute to the jQuery project--the documentation is simple and a lot of the methods (e.g., show, hide and append) are very intuitive.