When Joss Whedon came in to finish directing Justice League we knew there were going to be some big changes. After all, the film underwent some major reshoots to change the tone of the film and make it lighter. According to a recent rumor from Batman On Film, Jesse Eisenberg's Lex Luthor has been cut from the movie.
In a recent fan Q&A with the site, they were asked how big of a role Eisenberg’s Lex Luthor would have in Justice League and this was their reply:
“He doesn’t have one. If he did prior to all the changes/reshoots, it was cut.”
This is just rumor for now, but I'd actually be ok without Lex making an appearance. Unless he plays a major part of the story, there's no point to include him. I hate when films throw certain characters just to throw in a character.
I have no idea if that's what they were doing with Lex, but if he's been cut from the film, his role in it obviously wasn't that important. We'll just have to wait and see what happens.