To me, the best course of action for DC would be to open with Justice League then spin out individual stories from there.
One key difference in situation between DC and Marvel is that people have a general idea of who each of the big players in the DC Universe are and what their powers are. Plenty of people would be able to identify a picture of Wonder Woman and know that she flies and is super strong, the Flash who can run at super speed, Green Lantern who has a ring that creates large green objects, and Aquaman who can telepathically communicate with sea life. The details of their backstories might be lost on plenty of them, but they at least understand all of the basics.
Therefore, establishing all of them in solo adventures building up to a big team up isn't as necessary as it was for Marvel back in '08 when people thought Iron Man was a song and Thor was simply a being from mythology. WB could have come right out of the gate with a strong Justice League movie that brings together all of these icons and allude to key plot points that would be fully fleshed out in solo movies in the following years.
People are going to say what they want in regards to DC "copying" or "rushing to catch up" irregardless of what plan WB went with, so it's not worth trying to dodge these people's comments.