It seems to me that Suicide Squad was DC's answer to the success of ensemble films that have gained massive success from Marvel, here's the problem, the DC universe is so broken up right now that there's no way they can get that success without getting some consistency.
This movie could have been so good, it SHOULD have been so good, the actors were pretty well cast and all did pretty decent jobs with the material they were given. But the character development was next to nothing, and no one could have expected there to be. What should have happened was more build up. Movies that described origin stories for a good chunk of the main characters so that we could care about them more. Sure, Deadshot loves his kid, and Harley Quinn and Joker are in love, but I would have loved to see more details. Also who cares about Katana? At this point, no one outside of comic readers, she was a pointless character likely introduced because of her sword but even then did absolutely nothing for the plot. I think the impatience of DC and Warner Brothers to get an ensemble movie out really ended up hurting this film. If they had taken the time to do it right then they could have gotten a significantly higher quality film.