I don't think King is bad. I've read a decent chunk of his catalogue and a lot have interesting ideas. I'm admittedly not the biggest horror fan (though it's because most is super trope-y, which he does tend to avoid), but I just really don't like how he finishes stuff.
This and 11/22/63 are two where I actually feel like there's a "message" and I feel were closer to being closed well, but I just don't like the actual execution of it at all. It reminds me of this one NFL game a long time ago. The Saints pulled off a ridiculous series of laterals on the last play of the game to score the "game tying" TD, but their kicker shanked the extra point and they lost in painful fashion. That's what the couple books where I feel like there's an actual theme do. They get you right up to the finish, then botch it.
Maybe I'm being too hard for whatever reason, because I read a silly amount of light/mediocre writing and almost never critique fiction, but he frustrates me because of how close it feels like he got to a great piece start to finish.