I think there's a lot more to the cities. The drugs that people have access to are in part so damaging to them and the community because they are entirely unregulated and sometimes aren't even made up of what the person thinks they are taking. This (is a big part of) what leads to the overdoses and addiction. Mix that in with the threat of law enforcement, job loss, and heavy social stigma, etc that prevents people from seeking help, and you have a recipe for disaster. Imagine if everytime you bought a beer you had to wonder if you could trust the seller, and whether it had methanol or fentanyl in it?

No doubt there would be some damage from libertarian drug policies, but it would look a lot more like alcohol does, which IMHO would be less damaging to society and people than prohibition and heavy handed legal punishments is. People do need help with alochol issues sometimes, and it does sometimes destroy lives/families, but we don't make it orders of magnitude worse by treating them like criminals. (although we did try it in the US a hundred years ago and it didn't go well like we thought it would).