Enter a descriptive title (above) relating to class RouteSubscriber, then describe the problem you have found:
The documentation for this class has one line of generic documentation that only says it subscribes to routes. This tells me nothing. It needs something else added so that you don't have to read the class's code to find out what it actually does.
It would be better if it at least said it provides dynamic routes, and better yet if it said it provides dynamic routes for theme administration.