We're not curing cancer in any sub genre of the mystery world. Call me a cynic, but I think most authors are motivated by potential sales more than conscience when they write about hot button social issues. And that most readers of these books are looking for a way to placate their own guilty consciences at not actually doing more to stop these injustices. Which is fine. Let's just not pretend these books provide more of a social contribution than romance mysteries.
All mysteries are entertainment, first and foremost.
The plots don't interest me. If romance mysteries deal with issues not important to you, or often feature plots you find boring - that's a fair call. We all have that right to pick and choose. And there's no crime in any of that. This sub genre is luring thousands of new readers to the mystery section for the first time, and they are sticking around to try writers in other sub genres.