^Well, at least Shyamalan had two good movies (at least major ones) before his decline began.
I feel that the problem is that too many directors today assume they're writers when they actually aren't. They're superb at creating visuals and composition and timing and directing performances and creating cinematically stunning work, but just don't know how to come up with a good story as a foundation for all of that. Actual writers are considered subordinate and expendable, because directors believe they can do it themselves. And so writing, for whatever reason, is the one aspect of feature filmmaking that gets neglected while everything else is done so well. And thus you get all these films that look fantastic but are just dumb or incoherent.