Here's a thing a lot of people don't know about James Gunn taking over DC films:
Warner Bros courted him for YEARS before he said yes. He was not desperately trying to get his hands on this, like some people seem to think. He only agreed once they had worked things out to the point where he believed he would have enough creative control to do things his way.
The plan for Gunn was never to do "MCU but for DC." He literally refused to take that job.