Django REST Framework: Generics or ModelViewSets?
Why there is generics if ModelViewSet gives same abilities and more?

Let me first rephrase the question a little more explicitly for you...
"Why are there Generic Views, when there are also Generic ViewSets"
Which really just comes down to a question of why REST framework supports both views and viewsets. Answer - ViewSets are useful for prototyping or for cases when your API URLs neatly map to a fixed convention throughout (eg CRUD style APIs). Views are useful for being explicit, or for cases when your URLs do not neatly map to a fixed convention throughout.
I use generics and plain urls for my REST API, but now I stuck with problem: I want custom actions, simple views to make some things with my models, like "run", "publish", etc.
ViewSet gives action decorator to create custom actions, but only in ViewSets, also, there is stepial routers, which gives us ability to simplify everything using railsish convention-over-configuration.
But I find that ModelViewSet gives us same abilities, as generics: full CRUD, serializers, filters, cusstom pre/post and queryset, so, it leads to question:
Why there is generics if ModelViewSet gives same abilities and more? What a difference?