"I never understood how JQuery and JS were just dumped the past 3-4 years in favor of all thse complex frameworks like AngularJS, Ember, etc..."

Well, you can't have Angular without JS so we'll focus on the point of jQuery here.

jQuery does a few things really well – so well that Angular itself uses jQuery (or jqLite by default). angular.element(selector) returns a jQuery object.

Angular also does a few things well. Code reusability and testability are much easier to achieve with Angular, in my opinion. Features like data-binding also help to reduce boilerplate code.