I didn't say deep, I did say dark. 2 reasons why it is dark in my opinion. Firstly, stylistically it is a moody and dreary movie. Palette is one, but the score, actor expressions, lack of light moments all create this mood.

Secondly, here you have an iconic hero like Batman trying to convince himself of killing another hero, Superman. On paper this is clearly a dark subject matter. You do realize dark doesn't have to be Blood Meridian necessarily right?

I haven't read TDKR but only watched the animated film a long while back so cannot recall the exact events. Even if they have similar ideals, it doesn't mean a conflict between them isn't possible. The conflict arises from Superman's place in the world and the type of mayhem he can directly/indirectly create. To Batman his existence is a greater threat than his rogues gallery. Maybe its jealousy or maybe he is concerned about his legacy as being the one who defeated Superman or whatever.

I am not defending the movie at all. Just stating that the premise had promise and felt fresh in 2016 for a superhero movie. Wasn't executed properly.