Couple things:
Inception is a movie bursting with ideas. It's not about the puzzle at all. The only question is, does the rather mechanical nature of the screenplay overwhelm the ideas and render the film cold? But it is not a gimmick movie the way, say, The Usual Suspects is a gimmick movie.
And Memento is even less a gimmick movie. Its structure is so beautifully integrated into its thematic core that I actually get personally offended when it is labeled as such.
The Dark Knight and Batman Begins demonstrate the Nolan that bores me. There is very little subtlety, almost no finesse. And while you could charge Inception with the kind of clunky expository dialogue that the Batman movies are littered with, I felt like in Inception that dialogue was in service of establishing the rules of the world and moving the plot, rather than being used as a crutch to outright state the ideas of the movie.
As for Tarantino: I don't get the charge that he is retreating into his movie-movie world post Jackie Brown. Most acknowledge Pulp Fiction as his masterpiece, but Kill Bill and Inglourious Basterds can relate just as much to real world things as Pulp can. Kill Bill is a movie that has two deeply personal relationships at its center. The breakup of longtime lovers, and the love of a mother for her child.
Basterds, despite its tone, despite taking wild liberties with history, actually feels remarkably alive, even current, to me. The blood spilled is not cartoon blood. It is not the blood of stock movie characters repurposed for a movie-nerd's fetishes. It's violence that an alert audience will have to confront, will have to gauge its own reaction to. (And you'll see the same thing, with even more force, in Django Unchained.)