DC easily should have used superman to be the starting point for their movie universe..
have villians coming out all over the place
have young bruce realize he's wasting his life and that he needs to get his act together in light of what had happened and what is going on around him.. then you could have barry allen doing a similar thing.. and you could foreshadow the research that goes into making cyborg, cyborg
but they could have easily looked at how marvel built up to the avengers and do origin stories for: superman, batman, flash, wonder woman, green lantern and aquaman
then you could introduce martian manhunter and cyborg in the films.. hell you could tie green lantern's origin or shazam's into the justice league movies
as you said the animated movies are on point.. and they could follow a similar path, where certain people's origins are tied in with those films.. the main guys you do their origins before in separate films in the build up to justice league