Today, you might think that jQuery’s practices are old, outdated and ugly. Well, most likely you are right! But this does not mean that jQuery is no longer a relevant library to front end development. Despite its decline in terms of appeal, usage and popularity, jQuery is indeed still heavily used and might still be important in the next years.
jQuery is still extremely important. The first reason is that developers that need to make highly-compatible websites need jQuery. Unless you want to figure out by yourself how to fix all browsers’ ways of handling the DOM and different APIs, jQuery is your best shot to quickly build ultra-compatible websites. This situation is quite different for web apps, though, as you may (rightly) not want to support all the browsers out there.
Furthermore, jQuery is also used in a lot of modern frameworks: all Bootstrap’s Javascript is built on top of jQuery, Angular can integrate it for its directives, Backbone depends completely on it (and on Underscore), Ember depends on jQuery too, and Meteor JS also makes massive use of it.
Another important reason is the massive number of great jQuery plugins available out there. While the number of Angular and React components surely grows up day by day, the amount of jQuery plugins we can use is extremely high.