Twigg seriously think about what you're saying.
WB was tops because of Harry Potter
If Green Lantern was a good movie and still bombed maybe your suggestion would make sense.
But Superman Returns was a much more grounded dark and gritty take on the character, it bombed because it wasn't a good movie.
Catwoman was dark and gritty, but it was horrible.
Every Punisher movie ever was dark and gritty, everyone of them bombed.
I can think of so many examples of dark and gritty films which failed, it's not a good way to look at improving a film.
Jonah Hex could have been a serious western, but for some reason WB added the ability to talk to the dead and dragon balls, you seriously think these same executives have any clue what to do with Superman, or Batman after Nolan leaves?
And again Avengers, the third highest grossing film of all time, was not dark and gritty, none of the Spider-man films were dark and gritty, the Fantastic Four films were not dark and gritty (they weren't very good either)........ But they all did well, and most of them because they were good films, not shoe horned into some genre.