It seems like a lot people are walking away from this movie thinking it contains some profound truths about the nature of existence, but it isn't really about anything other than its own arbitrary, complicated rules.
Yes thank you, that's it. The movie exists for the sake of itself, in order to give Nolan material to put his intricate framework around, but the actual substance is threadbare.
When a person goes to see the film again, they can't help but merely analyse its structure, and that's it. Everything else in the film is simply there to give the film (in essence, this structure) something to do.
the story of DS9's "Trials and Tribulations" was merely an excuse for the episode to exist, for it to work within the framework of an older episode. Same with Inception
, it works solely for it's own good, and there is no movie left to take away in your heart when the film is over.