Cable cars, trams, busses, trains, taxis – if SF and Seattle have poor public transit, I've never seen a place which does then. And I say this as someone who lived in and extensively used said public transit in both cities.

Let's hypothesize about a utopian city where a person's housing is, at a maximum, a quarter hour walk/bike from their job at Apple. The moment that person switches jobs to Google, however, they have to choose between moving or losing every benefit the utopian city layout has provided. Worse, their new commute would be explicitly working against the design of this hypothetical city.

Workforces should not be (and are not with suburbs) tightly integrated into where they work. This is something important to consider. You can't have the same density of employers that you have today if you're also packing in the other services (residential, markets, drug stores, laundrymats, etc).