Yeah it's a bit bizarre hearing people say "this could never work", and them not understanding that it has "worked" this way for most of human history.
For most of human history humanity did not exist in the form it does today. There are regions in countries with higher population than the entire planet a few hundred years ago. So I don't think we can take much lesson about scale from the past.
I think you're missing the point. The scale of today's cities IS the root cause of the problems.