There was moment when I wondered why this got so much hate. It was at the beginning when Batman fights parademon at Gotham. It looked interesting. Then Batman calls Alfred by his real name next to criminal who hears the whole discussion. It wasn't only time they used real names before other people. Superheroes have this secret identity thing. That is why they use masks. Calling each others with real names this often makes their identities not so secret in short time.
Steppenwolf is worst villain of all the time. He didn't have any personality. I have no idea what his powers were. He just wanted to destroy earth. He reminded little bit of Sauron from Lord of the Rings movies. Sauron works because he is mysterious. He doesn't say anything. Steppenwolf talks which destroys the character. His voice doesn't suit the looks and words doesn't suit his actions. Everything not Sauron ruined the character.
Story and characters are all over the place. Dialog is terrible at times. Character arcs miss parts where they decided to join the group. Flash doesn't even think when he says he wants to join. I honestly don't remember when or why Cyborg joined. Aquaman joined after they lost their motherbox. He just appears when others fight Steppenwolf. Characters just do things and say words.
Batman's suicide mission at the ending wasn't built at all. He made plan which would have killed him if others had followed his plan. There was no build up Batman being suicidal. Wonder Woman told others to save Batman. Otherwise he would have died fighting group of parademons. This is not my own thinking. Movie says this. I haven't seen anyone else complaining this. Maybe because it was during the best part of the movie.
Ending was best part of the movie because the action worked. I wish I cared about these characters. They worked together and used their powers. Other action scenes worked if you didn't think too much. Amazons had stupid way to shut doors to their motherbox vault. Shutting doors meant six people had to starve to death between closed doors. Two of them got easy way out because they closed door too early and they had to keep the door open long enough to their leader to escape. Then they were crushed under stone door.
Justice League is a mess story and dialog wise. I can understand why Ben Affleck wants to leave after I heard the lines he had to say. Movie looks good and action scenes work mostly. There were couple posing parts which I didn't like. Movie is step up from Batman V Superman but nowhere near to Wonder Woman.
And Henry Cavill's upper lip thing. I noticed it in first shot but not after that. Maybe I had lost interest at that point.