If they need 600 million they are definitely limping towards the finish.
It was meant to follow up a critical disaster of a film whose only success spawned another movie (Wonder Woman) that was connected to it so much that if you skipped the framing device you miss nothing. So going in; your prior two movies are divisive to bad, and your only real success spawns from a glorified cameo. Not to mention that BVS was even hurt by its competition who did a much better job tackling similar subject matter. So with response to what was going on behind the scenes with reactions to Marvel and the GA you also end up with a director who suffers an awful tragedy who has to be replaced but also has a tonal difference.
So a mixture of a lack of faith in the brand, a competing franchise that tends to make better decisions, a competition who already hit that milestone 5 years ago, following up on one of the biggest disaster of your brands life, with two directors of different tones, and you expect what?
I'm not sure if anybody could've saved this, it was just way too early and a bad time for Justice League. No amount of reinventing the wheel would've changed the time frame to make it especially with all that went on during production.