Well, it’s not that they’re dead, but I think it’s really hard to make something cool because the quality bar is so high. It’s as if everyone’s seen it all and is a bit oversaturated.
But I could be wrong, of course. There’s an interesting counterexample. Sokobans never cease to amaze, and almost every year there are really interesting examples of the genre, even though the genre is 40 years old and it seemed like everything had been done and tried long ago.