Your code is always one new feature request away from needing "just a little more" from your front end. Before you know it, your nice and simple JS has to keep a lot more state than you anticipated. jQuery helps, but I eventually realized that it just helps write apps which do aspect-oriented programming on the DOM — and that is completely unsustainable for any but the most trivial app.

Angular has been a breath of fresh air in comparison. It significantly reduces complexity. It's also easy to add to an existing project, even one with server-side templates. At this point, however, I consider the use of jQuery and server templates an antipattern at worst, and a necessary evil for some types of performance optimizations at best.