Simple fix, raise gas prices to the point where people live and work in their community. St. Johns Town center is its own community. You could live, work, shop and never leave it. You could do the same downtown, with the Winn Dixie there. At some point, you can do the same at Cecil Field when it is fully developed.
I think we have communities all over town, but we don't see them for what they are, a community. If all of my needs were met for shopping (and I could shop online to augment them), I could live downtown, but I choose Avondale, which is its own community as well.
The people I really feel sorry for are those who live in a subdivision with one way in and one way out, or one of the first Ramsgate in Mandarin. It had over 1000 households with an entrance on Mandarin Road and another on Loretto. All zoned residential, so you had to travel to work and back, shopping when it was built was non-existent (although there is more now in Mandarin), but developers built this place back when Jacksonville growth stopped at I-295 and SR13. This was back when the developers really had no vision, other than money in their pockets.
Now, when I think of Palencia, there are shops, commercial, and restaurants all in that small area, same with Nocatee, there are communities everywhere if you look for them. But a lot of the old communities were built without ANY vision and only built to house people, as if no one could have predicted that business would move from downtown?!