If DC had thought about that years ago, back when Wonder Woman and The Flash were still in their writing phases and Batman's newest incarnation had only one film, then maybe they could've made it work. But I think it's too late, now.

I think it just comes down to some bigwigs seeing how much money Marvel Studios made and questioned why couldn't they cash in on that while conveniently ignoring how much time and work Marvel would've put into the creative direction of the previous Avenger related films.