>>128415438King's Batman was dying, Superman was mostly stuck either dealing with the New 52 plotlines or doing storylines that were forgettable and overall inconsequential.
The worst offender was probably Doomsday Clock. It was the storyline to get into Rebirth, affecting all of DC's mythos but the delays forced them to go into another direction. One that needed 0 care for DC's mythos, introduce new OCs and make Batman the center. Why try to write a story that demands care and attention to detail to middling sales when you can slap million versions of Batman fan fic into an easy to sell mega event.