Poor reception is probably what doomed it, as well as other factors that many others have mentioned like DC's shittier efforts (BvS and SS). This was the same thing that killed Baywatch and Pirates of the Carribean: Dead Man Tell No Tales opening weeks.
Superhero shows are trash
It’s very easy to determine what went wrong with Justice League’s box office performance. Simply put, not enough people forked over money to see it. I’ll take my Captain Obvious hat off for a second and give my two cents on what I think they—WB/DC’s executive heads—should do moving forward.
1) At the heart of it all, prioritize your characters. I liked Justice League because they finally got the characters right. Not just in terms of presentation, but in their characterizations. If Superman looks like Superman and behaves like Superman, then you’re getting my money. Don’t even think about the script until you have your characters primed and ready to go. It looked like that didn’t happen until the mid-filming/post-production phase. Better late than never.
2) Reconsider telling origin stories by first creating a demand for one. Mystery and suspense is what makes any story intriguing, but it’s not what defines these characters. Reveal their origin tales only if it adds anything of worth to the overall narrative. I liked Aquaman in this movie because I didn’t know much about his history. Now I’m intrigued; now there is a demand. Give me a little bit of what I want while simultaneously delivering so much more. No matter what you do, make sure the character’s journey runs unabated.
2.5) Please, please have a solid plan. All the stories happening from behind the scenes makes me think they didn’t prepare well.
3) “Aim small, miss small.” Look, world building is fun. It’s the reason why we’re here. But we need to stop planning for that sweet ass future, because there’s no guarantee we will ever get there. At the same time, I get it—a cinematic universe is much more fun, exciting, and profitable. All the more reason why you should never, under any circumstances, compromise the story of a film you’re working on in the present for an imaginary list of films you haven’t even made yet. Current film(s) in the here and now take priority. Always.
4) Consistency is key. Your actors are the literal faces of your stories. We want to keep them in the game from the beginning till end, with very few exceptions. When you bring them onboard, make sure they’re bringing more than just their acting abilities. Are they talented in other aspects? Are they great collaborators? Great! Utilize their talents.
5) If you have an overarching plot, cool. Keep it subtle and simple. Make sure it remains in the background. Only when you combine all these films together does the connecting pieces come together. But you need to earn it.
LOTS of reasons...
1) Bad reviews.
2) Zack Snyder.
3) WB Interference.
4) Bad release date.
5) Not a very memorable movie.
It's not a Snyder film, so that's a giant thing in its favor.
That shouldn't be interpreted as me being optimistic. I didn't like Wonder Woman either, but given the critical and popular reception of that film, I have to assume that's on me, and not the film. Still, I doubt Aquaman will work for me personally, but I think that it stands a good chance of doing well.
Superhero shows are trash
See, I hated Ezra Miller from jump street, so his/their protrayal of Barry as this awkward, unintelligent (I hope this is East) clown really irked me lmao. They basically Felecity Smoak'd his ass. Have him stammer a lot like, "Er, um, uuuuh", high voice, quick speech patterns, and silly facial expressions. I'm just not a fan of that kinda character type, so for that to be the comedic crutch wasn't doing it for me.
Superhero shows are trash