The mastermind behind most of the DCEU is Zack Snyder. Years ago when Justice League came out, his version of it was dropped because he had to leave production due to a family tragedy. He had tried for years to get Warner Brothers to release the movie and now with HBO Max they finally have done so. But many years after the fact and at about four hours long, was it worth the wait?
Both versions of Justice League feature a very similar story. After the death of Superman, Bruce Wayne knows that Batman and Wonder Woman can’t save the world on their own. So they must go out into the world and find more people with good hearts but incredible strength
Steppenwolf unfortunately arrives on Earth before a team can be formed to counter him. Since the world no longer has a Superman or even a Green Lantern, the only being capable of standing a chance alone with him is Wonder Woman. And even her odds are pretty slim.
But Batman will soon find enough superheroes to make a decent team. They will find the Flash, Aquaman, and Cyborg to join their ranks. But trying to revive Superman will definitely help save the world.
I will say that this version of Justice League is a good bit better than the original. I really had no idea that about 80% of the movie was different. But I will say that Zack Snyder would have never had gotten Warner Brothers to release a 3 hour Justice League in theaters let alone a four-hour one. So this was probably the best he could do.