This is source I found from another site, main source you can find in last paragraph
A passionate spark of frenemy-bromance between the Man of Steel and the Caped Crusader was famously created in the last DC adventure, Batman Vs Superman: Dawn of Justice, when these two legends discovered their mums had the same first name: Martha. That somewhat anticlimactic coincidence was widely considered to be indicative of something unconvincing in the whole project. The problems are still evident.
This new film has had a troubled passage. Its original director, Zack Snyder, had to step aside after a family tragedy and Joss Whedon took over, reportedly reshooting between 15 and 20% of the film, a segment which may or may not have included the ending. It’s an unhappy state of affairs that may account for the film’s tendency towards shapelessness. Or this may have been a function of the ensemble structure and an uncertain handling of Batman’s new, more respectable and collegial role within the League.
We are now a few months on from Superman’s awful fate and huge, sombre banners hang on public monuments all over the world, including Tower Bridge in London. People everywhere are thoroughly depressed and demoralised. Then it becomes very clear that a terrible new threat to Planet Earth is materialising: a grotesque force of evil and destruction in the form of Steppenwolf (played in digital motion capture by Ciarán Hinds).
Bruce Wayne (Ben Affleck) who in costume and mask is still being called that primitive prototypical name “the bat man” and still going into the deep voice, even in front of people who already know who he is, persuades Diana Prince, otherwise known as Wonder Woman – and enjoyably played by Gal Gadot – that a crack new supergroup should be assembled under their joint command. Metahumans need to be recruited. They will be the lightning-fast Barry Allen, or the Flash (Ezra Miller), the technohuman hybrid Victor Stone or Cyborg (Ray Fisher) and Arthur Curry, or Aquaman, played with muscular and humorous panache by Jason Momoa, from Game of Thrones. He is the kind of exotic undersea creature that David Attenborough might discover in Blue Planet II.
Meanwhile Lois Lane (Amy Adams) mopes listlessly about the Daily Planet newsroom doing dull human interest stories and Bruce’s manservant Alfred (Jeremy Irons) is even less the traditional below-stairs figure of old, now more a silver-fox computer whiz who says things like: “What the hell?” But everyone must put aside their differences and worries to fight together against the wicked invader – in honour of Superman.
Source : https://www.theguardian.com/film/2017/nov/15/justice-league-ben-affleck-dc-comics