I think people have forgotten about all the things learned from cohousing. I once lived in a condo complex originally designed to be cohousing and I knew lots and lots of my neighbors. Shared parking with a common path and kitchens facing the path with gardening areas goes a long way. Add in the shared common areas which were designed to force everybody to pass by, and it was routine to meet and get to know neighbors. (Then there are all the Christoper Alexander ideas that could be tried too.)