To be fair to the poster, Afleck's Batman (while a good action performance) was 'brooding and dark.' Likewise, the Superman we got in this film, for as little as he even had dialogue, was 'brooding and dark.'
YOU are RIGHT in that 'every character' is absurdly broad - Wonder Woman had some dumb film moments and was stuck in an awful idea of a designer gown at one point, but she was in no way 'brooding' nor 'dark.' On the other hand, she gave no indication that she was ambassador for peace, or any of the other characteristic Diana traditional has in canon. Another good example of how she was poorly served is in lines like, "Little boys have no inclination to share." There is really no sensible way that the scriptwriters or directors could think that this is would be some sort of post-feminist Strong Woman slogan for her that fans would appreciate and enjoy when really it's more of a comment about how 3/4ths of the films set-up and denouement was stupid and needless - particularly given it's placement in the film.
We did get, in some senses, a darker Alfred but he was far from 'brooding.' Irons was the real bright spot in the movie and even where they changed him from canon (essentially giving him the Oracle role and making him more front and center and directly involved in Batman's mission here), those were all positive changes that Irons carried forth brilliantly.
OTOH, Batfleck was pissy, dour, easily manipulated, petty and tedious. Cavill essentially had no dialogue and what he did have did more to pass him off as ineffectual and pompous: "the bat is dead, bury it. Consider this mercy." or dispiritedly morose about himself, his future and his adopted planet ("Righting wrongs for a ghost, thinking I'm here to do good. Superman was never real. Just a dream of a farmer from Kansas.")
Luthor is given a bunch of bunch of sentences to others that feel like he read some WIkiquotes on various topics that he REALLY, REALLY liked.