DC won't make a truly entertaining movie without a complete re-re-rethink of everything.
1. Too serious. Refuses to poke even a little fun at itself and make viewing fun. These are magical people in leotards, after all, not epic Germanic opera.
2. Often too visually subdued, muted, dim or dark. Hasn't fully shaken off Burton. It's an old look now.
3. Tone is too gritty, too "real," carried over from Nolan. Find something new.
4. Characters are generally ridiculously overpowered. The recent energy-projecting version of Doomsday is the most absurd example ever. Metropolis fight with Zod was way overdone.
5. Infatuated with its own mythos. Yes, we know why Batman is partly deranged. We've seen his folks murdered a dozen times already. Yes we know that Superman is always angst-ridden, insecure and afraid he can't fit in...oh wait, that's the current one, Superboy. Christopher Reeve's character outgrew daddy issues and teen angst as a teen and learned who and what he was. Confidence vs lack. Adult vs teen.
6. The characters generally do not resemble authentic, developed, complex people (thus interesting and sympathetic) the way Marvel's usually do.
7. Increasingly blah music (in fairness, Marvel's music has been pretty blah from the start...DC has the edge here, barely).
The JL trailers indicate they're already cloning elements that work with Avengers. So there's that.