But those suburbs already exist. What should we do for all of the people who already live in them? (And keep in mind that there's usually a good reason that people chose to not just live in an inner city in the first place.)
ST are quite explicit that they mostly don't think that retrofitting suburbs should be a focus, because they believe that most of these will go bankrupt anyway, given a sufficient amount of time (because of too much infrastructure liability compared to the tax base), and indeed this is starting to happen all across the US. Hence their focus on areas with a solid core already, that should then be strengthened and encouraged to expand organically from there.
The only thing ST says here is "let existing suburbs be what they are", which sounds like what you want as well.