In my head the template for Shyamalan's career is George A. Romero's masterpiece Knightriders: a film, a genre film, that is baldly ludicrous on its face ... and yet taken so seriously that it arrives at a certain admirable, mesmerizing intensity. But wait—can't zealous, solemn, deliberately meaningful genre films be a buzzkill (to say the least)!? Of course, of course. Obviously. But I'd say there are two broad kinds of elevating seriousness open to the mere genre entertainment. One is externalizing, communicative: communicating above and around the trappings of "genre" or "entertainment" to impart a series of messages or postures. (The sort of genre film that tends to win awards & critical hosannas.) Another is internalizing, an invitation down a rabbit hole.
Shyamalan often works on both registers, I think it should be admitted. The most ferocious critics of Signs, for instance, focused on the cheapness of its New Age nondenominationalism, the gracelessness (or unconvincingness) with which it peddled its "signs" and coincidences. Quite guilty! At the same time, the singlemindedness with which Shyamalan pursues his themes and expresses his stylistic tics also has its virtues. I don't know that I'm very interested in making (or reading) a case for Shyamalan as "auteur" that identifies his consistent themes, as these are, in his case, merely obvious, repetitious. But the way Shyamalan (consistently) constructs timing, line delivery, perspectival planes, the "weight" of the image (Ignatiy Vishnevetsky, in one of the very best commentaries on MNS I know, says "When the camera is stationary, it isn’t resting, it’s bolted down.") ... these things are fascinating, and possessed of an integrity of their own.
I can understand why someone would say Shyamalan's cinema is ultimately bad. I wouldn't even necessarily disagree with them. But I can't understand anyone saying they can't see anything of authentic and rare interest in Shyamalan's cinema. None of Shyamalan's work is as good as Knightriders; but aspects of it are far above 90-95% of what else is getting made in Hollywood. There's the intensity of focus, the sheer glee in working with 'restricted' elements (e.g., color palette), the willingness to create nonsensical stories and premises with ordinary heroes (Shyamalan's people aren't ubermenschen or anything of the kind, whereas a Bruckheimeresque blockbuster is populated by gifted experts of mind & flesh).