So, Dick, you don't think that genres sometimes should change? That they should stay stagnant? This seems silly to me, as definitions of nearly all things change over time. Mystery is a relative newcomer to the genre game, anyway, having started "officially" back around Poe's time. Who says that a vampire detective can't be classified in the detective genre... oh wait, it can't because the protagonist, not the plot, determines the genre. Except, again, over in Romance, it's the plot (romance) not the characters (vampires, werewolves, etc.) that determines genre.
But, again, I think that things are bit stuffy over in the Mystery genre. Maybe it's because I'm a young'un who loves the idea of mysteries but rarely finds books that ARE willing to break out of the conventions. Just because something has always been done a certain way does not mean is the only or even the best way to do it. As the old readers die off, it's the young readers who are NOT flocking to the old-school mystery stories...