> Cities used to be filled with tight knit communities in neighborhoods where everyone knew each other. Kids played outside and roamed around and no one cared
There are many neighborhoods in cities and towns in the US where this is still true. I know because I live in one, and I've visited others. There are also a ton of US suburbs and exurbs where people barely know their neighbours.
Having a friendly neighborhood has much to do with the strength of community institutions and the existence of "third places". Those can be present (or not) in a variety of community layouts and densities.
My take is that it requires a sweet spot of economic security where people aren't struggling so much that they can't/don't trust in community, but also aren't so wealthy that they don't need/rely on their community. Beyond that, it also helps to have physical layouts that enable friendly unintentional encounters between residents.
The problem is that none of these places will be cheap to live in, because all else equal, the existence of that lifestyle will drive up demand (and therefore housing prices).