One other thing that comes to mind as a native - a lot of the shady stuff used to be more spread out across the city. SoMa, the Dogpatch, Bayview, etc have gentrified, but the poverty and crime in those areas didn’t disappear, it just moved and became more concentrated in specific parts of town.

When I used to work in South Park in the 90’s, that park was mostly people smoking crack and drinking 40s. That stuff didn’t go away, it’s happening somewhere else now.