system
Given the following post, respond as if you're commenting on Reddit:
human
[Injustice 2] Why not ask the Prime Universe for help?

So, in injustice 2, Brainiac is coming. One of the big conflict in the plot is whether to release the tyrannical Superman to help, risking him taking over, or not, and fight Braniac without their heaviest hitter. It's a real dilemma. If only they had a backup Superman, you know? Like the one they summoned during the last crisis?

They know Earth Prime exists- they've already summoned heroes from there, and in Aquaman's ending he goes there. It's the DC universe, they'll find *someone* who can dimensionally travel. And while I'm sure the Justice League probably don't want to be called over for every minor issue, I'm sure any annoyance would be overshadowed by "GIANT SPACE SKULL SHIP EATING CITIES HELP". They are, after all, heroes, and they know this world has limited abilities to protect itself at the moment.

You get the help of a genuinely heroic Superman (and Wonder Woman, Flash, Cyborg and so forth to boot), the Regime stays safely imprisoned, everyone is fine. So why not do it? Why not at least consider it? You need help. Why go to guy who burnt a child's eyes out when you can step through a portal and get his heroic twin to help?
gpt
IIRC: The heroes don’t find out Brainiac is behind all the supervillains until he’s already almost arrived. By then, its too late to start experimenting around and trying to jump into the Prime Universe. It’s not a full proof method and even if you do get there, how do you know they’re not dealing with their own big problem? Yea, the payoff is big, but if you mess up you’re taking at least one of your most powerful heroes out of the fight to try to get allies. It doesn’t help that half the justice league gets brainwashed by brainiac at one point or another.

Better to just release Superman and keep an eye on him (which Batman does the entire game) than go on a mission that might fail.