I actually thought the fact that they tried to differentiate themselves from Marvel by having all their movies being dark and gritty was the biggest problem. Along with being actually physically dark to the point you can't see what's happening. I would follow the early Marvel pattern of each hero having his own story style for individual movies, with rare teamup movie. Batman movies should always feel a bit film noir and Batman should get his hands dirty on occasion. But heros like Superman or the Flash should have fun and uplifting stories and should always find a way to be fully good.