The plot had some very fulfilling and original contours to it, yes, that's what I thought made it great at first. But the real core of the movie is a series of gentle interactions. Each one is about drawing meaning from what does *not* happen. Less is more. Ivy to Lucius: "Sometimes we don't do things we want to do so that others won't know we want to do them." She's not telling him she loves him, only how she knows he loves her, which amounts to the same thing. But you don't really know she's right until you hear Lucius tell the same principle to his mom, to explain how he knows his mom is loved by Edward. Later her test of the principle, and her sliver of a smile, gives her secret away too.
Less-is-more is also part of the primary plot. The fear that grips the village, particularly the children, is amplified by the scarcity and subtlety of interaction with "Those We Do Not Speak Of". Ha, even that name attempts to say more with less. But the REAL moral of this story, and the whole purpose of the village, is to provide a space for moments like Ivy-Lucius-Alice-Edward to happen. For less-is-more to distill the human spirit to purest essence. Every great movie is made great by a few moments. Seconds out of hours, opening up human vastness. To say Shyamalan crafts them masterfully is saying too much. I wish I could say less.