I don't know why people call it 'grim and gritty' when it is most certainly 'Grounded'. Its a more realistic taste, I mean batman isn't killing dudes in cold blood and neither is superman.
Similarly, I don't mind this aesthetic because...I like variety, if anything I'm getting a little sick of 'tried and true' 'bright and happy' marvel films, because only once did I ever see consequences in those movies, and even then it was short lived and no where near the depth the issue needed to be dealt with (Stark's PTSD in iron man 3, fwiw). The irony is that Marvel heroes are the 'grounded' ones with all the 'consequences' at yet the definitely play out like what DC is commonly associated with. And yeah, DC has more or less gone the Marvel route, where, despite the heroes best intentions, sometimes the fallout is negative.
Its a role-reversal, and I think most people with only a casual appreciation of super heroics won't see it.
I don't want ALL 'grounded' films, I still love the Avengers, but it won't be long before these things become paint-by-numbers outside of Origin stories (which are in-and-of themselves paint-by-numbers). Avengers 2 'spoiler' they team up to beat Thanos.
OT: I think Bob hit the nail on the head,Twice. Superman is a polarizing character, you either love him or hate him, Take his 'boy scout' or leave it. So the film already started with legions of angry nerds. Secondly, hes right in that the movie was leading up to something grandiose, and then forgets it completely and goes for the slug-fest all-out battle climatic ending. I didn't mind the ending, or the action, and hey, you might see it as 9/11 allusion, that event is going to inform Movies in general for YEARS to come, whether we like it or not, events like that inform our art whether we like it or not, on purpose or not (and its pretty easy to find other examples). So I just live with it.