I think it's a matter of expectations. I liked Liam in 1st part. Joker was deadly in second. Bane is very good, but this is third installment I think expectations are big.
I think the film's biggest problem was that they were trying to make it BIGGERBETTERFASTER than the previous two, and ended up trying to do too much and going too far over the top. Bane's plan was implausible to say the least, when you consider the logistics of holding the equivalent of Manhattan Island hostage for five straight months without somebody
on the outside (or the inside, for that matter) figuring out a way to thwart you. The Joker's crazy schemes in the previous film were just on the other side of believable, but suspension of disbelief was rather more strained in this one.
It also made the people of Gotham look like a bunch of dimwitted sheep, but that's nothing new. And were the cops trapped in the sewers for all that time provided with hair clippers and shaving kits, as well as food and water? I dunno.
Really, I think Bane finally got the depiction he deserved as the one guy smarter and stronger than Batman. Even if, you know, he sounded like Robot Sean Connery.
With shades of Cyborg Peter O'Toole.