I still use Backbone.js. Why? It's more flexible than frameworks like Angular, React, ... because it does not provide a structure. Backbone is more a toolset than a framework. I have to think about my apps structure. I am the architect ;-).
In my eyes this flexibility of an toolset is an advantage, for many others it's a drawback. I like the idea to be able to set up my app from scratch.
As a JS developer i try to be independent from any framework. Frameworks come, frameworks go. If possible, i try to use pure vanilla.