That's not true.AngularJS allows a total an clean separation between AngularJS and your code through dependency injection.
It means that your code can be totally decoupled from the framework (even the directives).
That's not the case for Backbone,Emberjs and others.Their first sin is the use of Active Record,which means vendor lockin,and over reliance on inheritance (Backbone.Model.extend ... )
A few month ago I had to make some business logic work in a webworker,without duplicating it ,nor using angulars,in an angularjs project. Because AngularJS uses an IoC container,it just worked,the only thing I had to do is to manually wire up dependencies,but the same code worked without a single line of Angular code.
That's the most important difference between AngularJS and the rest,easy opt-out. And I really hope the javascript world begins to embrace inversion of control ,because frankly,i'm sick of all these spaghetti code apps, I have to maintain. Only AngularJS gives you the tools to write clean and decoupled code without verbosity.
Backbone and Ember suffer from the same "rail's way" problem.AngularJS is a good compromise between configuration and conventions without Active Record .
People often say Backbone is "lightweight" ,actually I think AngularJS is lightweight compared to Backbone,and that's why it is so successfull, with one lib, one gets everything one needs to build small apps as well as large apps,without all the boilerplate.