Not something I want to really get into, but I do believe the films shortcomings has come from many different things circulating the movie alone and the movies that came before it, in which I feel I need to give context and clear the air a little.
For example, Man of Steel opened to mixed to Positive reviews. The film was divisive between critics and fans. A really good film but the story was slightly hammy as certain characters were not portrayed accurately and the execution was just OK, albeit, some things never explained.
Four years later, Batman v Superman came out to very mixed to Negative reviews by critics and fans. A film with great potential, but the execution was terrible. Two of comics greatest and most iconic characters in a film together and the film was not as great as it should have been. For the most part you'd enjoy moments of it, but the story and the third act was not great. This was not well received. Not to mention the terrible trailers.
Within the same year followed Suicide Squad. A film which could have been told in a different way. A film which was actually decent-ish, but had problems that weighed almost as heavy as the good elements of the movie. This meant that critics and fans generally liked it, well better than WB's last Comic book outing, but the problems were there. WB wanted re-shoots. WB wanted to change the tone thinking it was the tone which was wrong with Batman v Superman. It was choppy. The jokes didn't all land well and the movie was all over the place tonally. It should have been better...especially with the final act. The cast were not the issue as the acting was good. A little annoying that it centred on two specific characters, mostly.
Then came Wonder Woman. A movie that basically did everything right from the ground up. As DC Movies have slowly got marginally better over time, Wonder Woman opened to really great and excellent reviews from critics and fans. Because of WW being such a great movie, WB decided to make changes to make her more front and center in this movie.
On top of the re-shoots and editing to make this film more attractive for all those who watched Wonder Woman, the tragedy with Zach Synder's family, knowing Warner Bros wanting to truncate their movie from 2hrs and 45mins to 2hrs, from knowing Henry Cavill had a moustache and it had to be digitally removed for filming the re-shoots, from learning that Ben Affleck doesn't want to play Batman any more and from Warner Bros being soo reactionary with all their previous comic book movies after BvS and not having someone like a Kevin Feige to take the lead and be the head honcho of the Franchise, WB would have always had an upward struggle with this movie and their predicted $110-120 million on opening weekend was never going to be met. Ever! Why? Because you did not control the narrative and you gave away too much of the film's behind the scenes problems. You have lost the trust of the audience, the critics and the fans. Batman V Superman literally made nobody care for them. Only a little trust was gained with the outcome of Wonder Woman, but Gal Gadot can only do soo much. Damn, Katherine Bigalow single-handed "Saved" WB.
Now with saying all this, is by no way a means to be a disclaimer to Justice League because the film is bad and you will not have fun with it and thoroughly dislike it, not at all. The film does have it's problems, but it is still a good film as like Suicide Squad, or should I say, unlike suicide squad, the balance of what is good out weights the bad, 70 to 30, in my own personal opinion.
Visually, the film is amazing and it IS just a fun movie at the end of the day, but with the current track record and the handling of this movie and everything surrounding it, it is probably best if Zack handled it. If it was a mess, then it's Zack's fault. This film reeks of studio interference and a hodge-podge of trying to piece together another man's genius and doing it wrong. Plagiarism at it's finest! It's a pity we couldn't see what Zack was cooking!