He’s not credited as the film’s director, but, y’know, would you want to be the credited director of Justice League?
You can blame a lot of the Justice League theatrical cut’s issues on Warner Bros. They’re the ones who took control of the project after Zack Snyder left the film.
Some of the fault also has to go to Joss Whedon, who Warner Bros. initially brought in to punch up Snyder’s vision with more jokes.
He reshaped the script and directed the reshoots used to rework the initial concept into the mess that eventually opened in theaters in 2017.