So which should you use? Well, let's compare using the three significant 2006 innovations of jQuery: easier DOM manipulation, AJAX, and animation.
jQuery gave us DOM referencing by CSS selector, and we were ecstatic. But ES5 gave us
querySelectorAll(), which outdid jQuery by additionally supporting all CSS3 selectors. Thereafter, DOM manipulation was at least as easy using vanilla JS as jQuery, and ultimately better with vanilla because the 100k jQuery abstraction layer wasn't required for the job. Vanilla JS 1, jQuery 0.
$.ajax() syntax in jQuery was indeed the greatest thing since sliced bread, especially its callback implementation. But there's a new sliced bread in town. ES6 gave us the indomitable
fetch(), Promises, and
await, which do a better job of handling not only AJAX, but any asynchronous task. Vanilla JS 2, jQuery 0.
I adored jQuery. It was great fun to use, and I was completely dedicated to it for about five wonderful years. But jQuery is now an obsolete library. Its spotlight has dimmed, its curtain drawn. Give it its much deserved star on the web technology Walk of Fame. But legacy code using jQuery should be updated, and no new code should be propped up by the jQuery crutch.