This is not a good film; I'd give it a 4/10. But I don't find it irredeemable.

Like other DC films like Suicide Squad or Justice League, if they just did another draft of the script and the editor did their dam job, it'd have been better. Perhaps not a masterpiece but...comprehensible. And shorter too. I always found it strange how they couldn't coherently tell a story the comics did so many times. Even the 90s cartoon crossover completed the same story in like an hour. And Superman survived too!
Batman and Superman think the other is dangerous. They have a fight. Turns out (insert classic DC villain) is the real threat. They team up and save the day. The end.
Heck, Marvel did a toned down version of the same type of story with Iron Man 2. "Friends that are superheros have a falling out but make up by the end to save the day". That's all they had to do. Not a 150 minute trailer for the next ten years of DC movies that are now up in the air.