"You do need density, even if it's local density."
This may be the most important lesson for reshaping cities. There is no need to make everything denser, or even to make most of the urbanized area denser. What is necessary is to create 'nodes' that are denser then the surrounding area, and the provide the correct infrastructure for that density. And hint, that ss not wider roads.
There are fundamental limitations on how dense automobile development can be. The rule of thumb I've heard for converting raw land into residential subdivisions is that 20% of the land will go for roads. When plotting a commercial center, every thousand square feet of retail requires about the same square footage. Developing at higher densities requires alternative modes of transportation. Amusement parks and airports understand this, and accordingly, make use of shuttles, trolleys, sky rides, moving walkways, etc. There simply isn't room for everyone to drive.