I think Nolan does care about depth, just not depth of character. Or, at least, not beyond the hero protagonist. Beyond Cobb, and to an extent Mal, none of the characters had any depth or were allowed to develop. That didn't mean that none of the others were entertaining or interesting, but that was mostly down to the performance, rather than any characterisation on Nolan's part.
I mean, surely disagreeing Fischer was thinly sketched by saying Cillian Murphy made the most of what would otherwise have been a one dimensional character is a bit... paradoxical? I agree, Cillian Murphy did a really good job with Fischer, but Fischer as Nolan wrote him wasn't a character that was particularly developed beyond the very bare basic journey he made over the course of the story arc he had. And the other supporting characters; Ariadne and the rest of the Inception team, didn't get any development at all. Which was a shame, because they hired great actors to play them.... and then didn't give them anything to do, beyond action scenes, except to spout expositional dialogue at each other (poor Ellen Page and Joseph Gordon-Levitt got that the most - and they can both be superb, but who would know it from this?) and occasionally dish out the odd for-the-trailer one liner.
I don't mean to be so very negative; I did enjoy the film, but I always prefer good characters over anything else, and I would have loved even a tiny bit more depth to the characters here, I think it would have made the film spectacular if only I'd been able to care about any of the characters. Because everything else was terrific.
Then again, I suppose it is first and foremost an action thriller and not Eternal Sunshine Of The Spotless Mind 0.2 with dreams, so maybe my complaining is just silly?