I don't think people give a shit about the gritty mcgrit grit atmosphere of the Daredevil/Batman series because that tone actually fits the characters. Batman is a morbid, humorless ****-face, as is all of Gotham. Same with Daredevil and Hell's Kitchen.
By comparison, Superman is not a dark, gritty character outside of a handful of alternate-universe/what-if portrayals. Sure, he's not sunshine and smiles all day everyday, but then neither is Captain America. Ultimately though they're both beacons of hope and goodness that are supposed to inspire those around them with their uplifting personas, and that same sense is supposed to bleed into the audience. Captain America achieves this in his movies, thus far Superman has not, and that's because his world is so ****ing depressing and cold all the time.
It just doesn't fit the character. Winter Soldier is all the proof you need that you don't need grit to showcase mature themes.