I really don't like WB's grimdark approach to DC. You just can't build an entire series, at least not a superhero series, to complete darkness. They need to have levity, moments of light and humanity so that the dark moments have something to work with. People say DC is trying to differentiate itself from Marvel, but Marvel isn't doing 100% funny stuff either. Their movies have drama, tension and sadness in them, because even they know that going entirely to one end of the spectrum isn't going to work. Anybody remember the beginning of Guardians of The Galaxy? Yeah, and that was their funniest movie to date.
That said, if there was ONE movie that I thought could work with this grimdark approach, it was Suicide Squad. This is a group of psycho criminals, under secret government contract killing other criminals. That could work, that COULD be a tragedy, that could go all the way to that direction and be really effective. There'd still have to be SOME lighter moments, but overall I think a dark tone could've produced something new, unique and effective. Now it seems they're backing up, trying to move the movie closer to the "center", an effort which I'm afraid will produce something average at best, and disjointed at worst.