There was a conspiracy theory I read about this, which would have been AWESOME, basically, these movies are part of the Christian Bale batman trilogy, the head of wayne enterprises is now Slade Wilson, and Slade has donned the mask of the Bat, but since he's Slade, he's willing to kill. I don't know, I would have been more okay with that than Batman actually killing people, isn't that Batman's number one no no?
It's a big aspect of Batman. Not that he's probably never done it, I'm sure there are notable instances, but generally he's unwilling to kill people and won't use guns. It was a HUGE plot element of Batman Arkham City, I believe it's a big plot element of the famous Killing Joke story (Getting turned into an animated movie soon with Mark Hamil and Kevin Conroy doing the voice, fuck it's going to be good), and even the comic this movie borrows a lot of its plot from, The Dark Knight Returns, has Batman making a huge tank to take on the gangs that fires non-lethal rounds. Even still, to do this is just wrongheaded to begin with, because in the previous movie, Man of Steel, they got a lot of flack over Superman killing Zod, and that one could be justified and had a huge impact on Superman's character.
As for reviewers saying it was boring, I think that's kinda wrong to say. To me, the movie was never boring, it had enough interesting elements and action strewn throughout that I was kept engaged. It's like the one complaint I wouldn't put on it, it's mostly just a mess with the story.
