Some exceptions aside, the original creators of most of Marvel and DC characters never got rich.
Some of them even died before the companies recognized their rights to get a mere fraction of the money their characters were making.
Most of film producers only care about money, money comes from tickets and subscriptions, and there are so many new movies around there that most of us always end up watching the ones from a franchise or film stars we like or we are able to remember.
So if an actor has good box office statistics, they pay him to be in the credits.
Anyway, I suspect that the real reason the film is tanking its because of quality, not moral issues.
But I haven't watched it (nor planning to), so what do I know?
@jordan
By the way, what a waste of talent: Brie, Baccarin, Elba...
But wasting talent is what Hollywood does.