To the degree Miami has avoided gentrification [and what was the demolition of the Orange Bowl but that?], it is because there are so many attractive alternatives for the gentry. Unlike San Francisco, most of Miami's border is just lines on a map. But for a roadsign there's nothing to alert the driver like a bridge over the bay.

Also unlike San Francisco, Miami grew around the automobile as primary transportation. Houses come with parking.

Finally, the primary attraction of Miami is water, and to the degree urban life is attractive it tends toward the velvet rope variety rather than slumming in shared public space.