Superman is canonically one of the most powerful beings in the universe, so writing an evil version of him is pretty difficult to fuck up. Superboy Prime's a bit of a whiner but mostly they pull it off fine.

Batman and Joker are decently trained but still regular people, and there's absolutely no justification to how they could ever beat up every other hero and villain in their universes, much less being some lynchpins of reality like what Dark Nights Metal implied. Both would be much more interesting if they were toned down a little. The Joker especially is fucking stupid nowadays: they should go back to him just being a funny criminal that does things for the lulz, rather than obsessing over Batman all the fucking time.

Also, Scott Snyder is a hack and has never written anything even approaching mediocre.

I feel DC Comics did the exact same mistake like Marvel with Absolute Carnage,an interesting take despite already done in the past in a different form but then did too much with it and stopped going for that premise and lacked any form of direction.