I had no problem with Affleck, Gadot, Cavill or Momoa in their respective roles. Eisenberg is not a bad actor but his interpretation of the role was completely bonkers - that is something a director should have fixed. He only played Lex Luthor Jr., as in not the real Lex but that kinda got lost in all the problems the movie had.
I`m not keen on Pattinson for Batman but if he does horribly, I`ll just shrug it off. There have been a gazillion iterations of the character, why should this one bother me?
However, I will give it a chance. There is "wow, that looks like bad casting" beforehand and "wow, this sucks" when seeing the movie. Some of the weirdest casting choices in movie history have paid off, some have not. Granted, Pattionson is the only one so far that gives me a "I dont know if I can buy this ever" feeling, didn`t have that with the others. My main problem with him is most really shallow: he has never done it for me in the looks department.