It's not AS BAD as people are making it out to be. Don't get me wrong, it's bad. But not that bad.
Spoiler free review - it's a hot mess. It was 4 or 5 epic plot lines loosely strung together without explanation. This movie could have been great if it tried to go 100% on 1 or 2 plot lines, rather than go 25% on 4 set-ups for Justice League.
Lex Luthor was......well, the worst part of the movie. His motives changed on a whim without reason. Wonder Woman, however, was BLODDY AWESOME. Diana Prince was lame, but when she put the suit on....ALL OF THE YES AWESOME IS AWESOME.
Ben Affleck as batman was actually great. Was truly surprised at that. But, the problem is, the way batman was writen in this film was all kinds of awful. He kills people now. Batman.....kills people....and uses guns.....because.....reasons? It's not really a spoiler because it's in the FREAKING TRAILER (tbh, if you've seen the trailer - you've seen the movie minus maybe 1 or 2 spoilers) of the hint that Joker killed robin. I'm ok with this story line - this batman has been doing this for 20 years and has lost all sense of who he is after he lost robin.......except, there was no explination. None. There's a very subtle hint....and I mean VERY subtle. When in reality expanding on that would have been a great story and shed a lot of light on why this batman is who he is. And we got no Bruce Wayne. None. When Bruce Wayne was out of his suit, he was still batman. Still on a mission. There wasn't a single Bruce Wayne moment in the -entire- film.
Superman was a dope. I'll leave it at that. The acting was poor and the writing did him no favors.