As of now?
Avengers-isms like Amanda Waller or Martian Manhunter forming the league. An alien invasion that is just in America or one American city
. An alien invading earth that feels like a villain Superman could take care of himself.
Snyder passing it off to a director who absolutely has no business touching a DC character, let alone half a dozen.
It just happens right after MOS 2 and that solo movie doesn't even have enough references to the other characters and no cameos to make us care about anybody other than Superman.
A silly team of villains as the threat.
A major role for Martian Manhunter or Aquaman when there's clearly not enough time to establish them when we have 4 or 5 others to worry about. So basically, some characters getting "Hawkeyed" would be a bad scenario.
Awful casting. For example Gina Carano as Wonder Woman. Armie Hammer/Jake Gyllenahaal as Batman.
Wally West chosen for Flash instead of Barry Allen. That would turn me off big time.
A version of Green Lantern who actually isn't Hal Jordan nor John Stewart.
Sequel bait. I don't mind Aquaman or Martian Manhunter appearing but not as major players or marketed in posters/trailers as team members. But it doesn't mean you have to do some cliffhanger to a sequel saying "oh theyre going to be added to the team in the next movie!" or "let's tease the next villain! OMG it's a shot of Apokolips and maybe Darkseid!!". NO! Put everything into the movie but without doing a full-on 7 members if that makes any sense. Make it a completely satisfying experience so if there never was another you're like DAMN im satisfied with what we got! That way it ends, every character goes off into their solo movies and a sequel doesn't ever have to happen. Then if they can crack another good story/threat that would make the League reform? Then bingo.
