The 1959 DC Comics version was military agents up against the fantastic. In 1987, writer John Ostrander retooled the concept as expendable supervillains conscripted into espionage for early release (a la The Dirty Dozen and 'Mission: Impossible'), led by the hardnosed handler Amanda "The Wall" Waller. The series and team went through five iterations over the years, eventually including variants on television ('Smallville', 'Arrow') and in this film.
The pieces were all in place. David Ayer, a great director best known for 'End of Watch' and 'Fury' was set up with a great cast, including heavyweight Will Smith, Hollywood up and comer Margot Robbie and Oscar winner Jared Leto as the unhinged Joker. Early trailers pointed to an irreverant film, with a distinctive color palette and gritty undertone, and a guest appearance by the Batfleck.
Ayer, known for well orchestrated character driven films, should have aced this movie. Unfortunately, studio interference, perhaps in response to Batman V Superman's terrible critical review (too dark, too sombre, too brooding) may have influenced the studio's move to get the company - that had cut the trailer - to recut the movie. Word is they mashed up Ayer's vision with the trailer edit and the result is a lightweight movie that flows semi-coherently through it's paces but ultimately is a bit of a mess and not as compelling as we would have liked.