[ghaff]

One of the challenges is that you have an existing city that isn't that. The towering skyscrapers at least are something you can implement in a relatively limited area a la classic urban renewal. (Which mostly doesn't work well.)

(But you'll find no shortage of people arguing for basically bulldozing the Mission and building a bunch of high-rises.)

The other has to be more organic but takes a lot of time and tends to generate a lot of resistance if 2-story zoning is turned into 6-story zoning.