There is a running joke between Marvel and DC Comics. Marvel is more light hearted and fun and DC tends to be 'dark.'
In Deadpool 2 Ryan Reynolds' Wade Wilson asked Josh Brolin's Cable if he'd come from the DC Universe because he was so dark.
With everyone excited about the SnyderVerse, there has been a lot of chatter about bringing it back.
The higher ups at Warner Bros don't want to continue down the SnyderVerse road because they believe it is too dark and not a direction they want to go in.
The want to keep the tone of Wonder Woman, Shazam and Birds of Prey.