15. Market The Movies Properly
The DCEU to date has had something of a marketing problem for its movies. While Man of Steel's advertising push largely went ahead without too many problems, Batman v Superman struggled to strike a consistent tone, and as a result a nervous Warner Bros. released different trailers playing up both the "dark" and "fun" elements of the movie. The marketing was also widely derided for largely spoiling the movie's third-act arrivals of Wonder Woman and Doomsday.
Then there's Suicide Squad, which rather cynically leaned on popular music to try and paint itself as more fun in response to BvS' criticisms, even as previous trailers retained a darker, more serious style. Also, many expressed surprise at how little Jared Leto's Joker was in the final movie given his presence in trailers.
The problem with trying to make promotional materials targeted at different subsets of the audience is that it suggests to the viewer that the movie doesn't have a distinct tone: is it grimdark or is it fluffy fun? If Warner instead made more cohesive trailers that at-once demonstrated the combination of light and dark, then viewers might have a better idea of exactly what sort of film they're potentially paying money for.