While one may not agree with it, this seems to be the direction WDW is taking with DHS:
Rather than being in (or pretending to be in) a "working studio" as if you are on tour of an Old Hollywood back lot and enter the studios buildings in which filming is taking place and you learn how movie magic happens; DHS is a place where you can "ride the movie," in that you enter the movie and, ideally, become a part of the story.
So, "studios" no longer refer to buildings in which movies and TV are filmed, but to the "production studios" that make movies (Disney Studios, Disney Animation Studios, LucasFilm Studios, Pixar Studios, Marvel Studios, Fox Studios).
The public space is still themed to Hollywood at various time periods. But the major lands and the rides/attractions are themed to a specific IP/movie/TV shows that you magically enter.
So, with regard to your gripe, what is happening with MMRR is that you are in L.A./Hollywood, and you go to the Chinese Theater in order to see a Mickey Mouse short, which is where Mickey Mouse films once premiered. And then, as you're watching the short, you magically enter the story and are part of the short itself.