Originally Posted by The Joker
Personally I think it's because it doesn't live up to the high standard Batman Begins and The Dark Knight set. It just doesn't match either of them in terms of quality, IMO. It's easily the weakest one of the trilogy. Not that it's a bad movie by any stretch of the imagination. I think it did break the superhero threequel curse.
The shine has been wearing off for a few months now, the negativity has been increasing, particularly since it came out on blu-ray/DVD. People have had time to sit down and watch it more in the comfort of their homes and see how flawed it really is.
For others, the months of watching it in the comfort of their own homes have only strengthened it. While some flaws from the first viewing are still there, others have sweetened with age. I used to have a problem with the pacing because of how unconventional the structure was, but now I feel the pacing works incredibly well and flows and builds in all the right places. The tiny plausibility errors no longer bother me, like his leg brace, back fixing, etc. They all fit perfectly in the world of the trilogy upon rewatching them all, it was simply my own definition of the reality of his world that was skewed.
I dunno, I think this movie has accentuated Nolan's greatest flaws and weaknesses, and is definitely not his best film, but because of how grandiose it is, it has to cut corners in some areas to make room for depth in others. I definitely think the high bar of the first two movies skewed people's expectations of the third film by misinterpreting Nolan's vision of it and envisioning something that Nolan never intended to do. That doesn't make the flaws of the film go away, but it certainly augments them because of unrealistic expectations. Like BatLobster said, for those who will watch it for years to come, the experience will be seamless between all three films, and the story will just be accepted as the story being told, which will hopefully stop people from having petty issues with it.
Just like BB and TDK have their issues but are amazing films and Batman adventures, TDKR will also stand the test of time in the same light. I think Joker's post above is very telling of that. He's been one of the most vocal critics of the film on this forum, and even he thinks it's easily on the positive end of the spectrum.