While I understand your point, this kind of marketing can be useful, even for informed listeners whose knowledge of certain sub-genres may be lacking. For example, I discovered certain artists through the "Legends of Acid Jazz" series whose records I many not have picked up otherwise.
Not sure if this qualifies as a "gimmick," but I am annoyed by these alleged "Blue Note" compilations that contain music originally released on Blue Note, Capitol, Liberty, Roulette, Pacific Jazz, and others. I'm glad that interesting compilations can be made from all this music with minimal legal issues, but it misrepresents the "Blue Note" brand.