here is an article perfectly explaining JLs failures....
"Occam’s Razor suggests that folks didn’t like Batman v Superman: Dawn of Justice so they stayed away from the sequel. Like Teenage Mutant Ninja Turtles: Out of the Shadows, a retooled, lighter, more kid-friendly “this is what the last film should have been” sequel was comparatively rejected because audiences sampled the last one out of curiosity and didn’t like it. If you consider Justice League to be the third chapter in Zack Snyder’s DC Films trilogy following Man of Steel and Dawn of Justice, then Justice League played like the third Divergent movie. Fans and general audiences decided not to be fooled for the third time."
"To be fair, it is entirely possible that the film will play well overseas (although $281 million isn't a huge global bow for a movie like this, especially if it doesn't leg it out). Speaking of which, it may leg it like Fantastic Beast and Where to Find Them. That J.K. Rowling prequel earned $234 million domestic from a $74.4m debut (a multiplier which would put Justice League just under $300m) and then $814m worldwide. Justice League was never going to play like The Avengers, and I would argue making it into a copy of The Avengers may have been a crucial mistake in a world where The Avengers is available on Blu Ray or VOD. But for now, Justice League may well become the biggest-grossing “bomb” of all time."