It also doesn't block well-known libraries. Using this addon sounds like a really good way to have a bad time on the Internet. By the logic of this, why bot block websites which have non-free content or other supporting files?

The whole premise of a website is that the owner gives you a licese of some kind to view it. Blocking only a technical part of it makes no logical sense. It's not like you are going to take the JS code under a free license that is likely dependent on the HTML structure under a non-free license and do stuff with it.