I lived in a few recently, after living in a detached house, and my experience was not as you describe. The buildings housed all ages and we were all friendly with each other, and if someone was in the shared outdoor space, a neighbor would quite often come to join them. In the building before that, there was no shared space, but everyone was friendly, no different than the detached house place where I live now.

Which isn't to say anybody should be forced into a multi-unit building and mixed-use neighborhoods. But as you point out, prices for these types of settings are often higher than detached homes, indicating that they are under supplied and more people want them then are currently allowed to live in them.