You are 100% right that the neighborhood feeling matters, but to be clear, the amenities need to come first.
I grew up in an apartment building that absolutely felt like a neighborhood in itself. There were at least 10 other kids in the 400-unit building my own age. In the local neighborhood (consisting of other apartment buildings) there were easily another 30 kids my age, any of whom I could see in a 5-10 minute walk. Few people owned cars (it was NYC after all!) and the area was quite safe traffic-wise.
I spent countless evenings outside walking or biking along promenades, or just hanging out in parks, playgrounds — all literally steps from my apartment building — and as I got older, in libraries, cafes, restaurants, shops, etc. The building I lived in also had a pool and multiple community “rooms” that were several thousand sqft large, which we reserved for birthday parties and other events.
It was fantastic. There were kids there because the spaces were designed to support families, and the “must have SFH with yard before having kids” attitude among the middle and upper-middle class is pretty weak in NYC, so my neighbors could be similarly-high SES because not all parents immediately flee apartment living for the suburbs.
Today, I live in a Bay Area inner suburb. There are, again, 10 kids my preschooler’s age in the local (couple blocks) neighborhood. But they can’t bike alone (or even walk alone, really) because drivers often hit 50mph and don’t look where they’re going. Each of our back yards — though we have one! — is tiny, much smaller than the community rooms I had growing up, so for any serious physical activity we have to get in the car to drive somewhere, contributing to the “traffic is a problem” problem.
The closest public park is a 4000-square-foot grass triangle in a quiet almost-cul-de-sac that takes 10 minutes to walk to and 30 seconds to walk across. There is a library 5 minutes’ walk away, and it is a saving grace.
If I could transplant the apartment building I grew up in to my local neighborhood, which is about 2 miles square — 100 million sqft — its 16000 residents could be housed in about 16 buildings, each of which would have a 25,000 sqft footprint, totaling 400,000 sqft and leaving 99.6 million square feet for fantastic parks, promenades, playgrounds, schools, trails, open space, basically any use you could imagine. Each apartment could be owned, 2000+ sqft, with private decks/patios/balconies and wonderful views.
If that were available in the Bay Area…we could build them at 2x the density described above and house the next 20 years of newcomers…