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It isn't only the twist, though, it's the timing of the twist. Plenty of movies with that kind of twist are re-watchable, but you have to put that twist about ... two-thirds, three-fifths of the way through. The rest of the film is devoted to the protagonist exploring the consequences of realizing that one of their big axioms was wrong. Shyamalan's timing puts the twist at the end, the characters don't really get to react, etc.