The problem with Metropolis being ruined is less about Superman allowing it. And more about the fact there is no catharsis in the movie over it.
we have him freaking out over killing Zod. we have a small freak out over his mom being in danger.
(where Clark totally murders like 20 people at the gas station)
People getting hurt is inevitable. Especially with a massive threat. Zod, Brianiac, Apocalypse. there will be casualties. No one expects him to save everyone.
superman being mr perfect and saving people while fighting is generally a given. and we never want to see him carelessness be the cause of an injury. so, its partially careless film-making here as well. why were those buildings occupied? why wasn't the city evacuated immediately? Synder intentionally had people stay in them for some odd reason. like the Daily planet, half way through the city being wiped out, finally saying, "hey we should leave!" lights on in the skycrapers. traffic on the streets.
This does make him look bad, as he did almost certainly get civilians killed for no reason. its pretty obvious after the 12th building, that smashing through buildings isn't going to stop Zod. so stop fucking doing it. The fight scene was poorly done. very repetitive like that.
Then again, at the end. no catharsis. the trillions in property damage, millions dead, and lingering terraforming is never addressed. you can't do that. your movie will feel hollow if you ignore things like that.
Show. don't tell. Serious flaw in the movie. we are told hes really human. hes from Kansas, S means hope, etc. None of these are really shown.
This is exactly why the original iconic image of superman putting the US flag back on top of the capitol was there. SHOWING hes an American. not telling us he is.
phantom zone is not shown at all. if this was you only introduction to it. you would have no idea what it was.