I see some benefits to the tight coupling between a JS client and the backend (eg: DSL fields), but are those benefits worth having such a tight coupling compared to REST (I realize this isn't called REST, but rather just CRUD).
A basic javascript library for doing crud operations against a Rails backend should come as standard with Rails. It's better than angular's services and similar libraries.
I never tried myself Angular and friends, only read guides and tutorials to get an idea of how they work and for sure compared to those this looks much simpler to implement. Nice one.