I look to my own state because it’s what I know. A city like Jersey City has an R-1 zone for it’s least dense zone. At a minimum, you’re talking two family housing. Replacing old housing stock is a process, and so while the zoning has changed to allow for greater density, it’s just taking time.
New York looks pretty good to me, and I think could be a model. I think even 65/35 would be a good mix of high and medium density to single and two family housing.
In regards to all these cities, zoning may be in place for SFH, but how old is that zoning? Some places just don’t update their master plans. And like I said, I can’t really speak outside of NJ because the law is going to be different anywhere. I like to think it’s just a matter of time before things get modernized, but I don’t know.