This doesn't require single family housing on giant lots. Just well built buildings with proper insulation and sound proofing. I used to think apartments were just noisy until my partner and I moved into our current place. I live on the top floor of a 2 building, 6 unit complex of loft apartments cascading down the side of a hill. The buildings had to be built to withstand the extremely strong winds from the bay, and as such they're solid as fuck.

Despite our downstairs being tile floor our neighbors have told us they haven't heard any noise from us at all. My partner and I started being less concerned about noise and began playing somewhat loud music frequently and yell to each other across the unit. Despite this our downstairs neighbors still haven't heard a peep from us. For a while I genuinely thought our neighbors were just trying to be nice as everyone in our complex is super friendly and gets along well.

One day our neighbor in the adjacent building was woodworking in his garage. Normally the noise wouldn't bother me, but I was focused on something so I shut the window facing the courtyard which made me realize just how soundproof this giant concrete building is, both between units and to the outside world. I couldn't hear our neighbors saw unless I opened the curtains and tried to hear it, otherwise it might as well have been very faint background noise. I really wish buildings like this were the norm for apartments because they provide all the privacy of a single family home with all the benefits of apartment buildings.

Issue is, these US-style lawns are often mandated in ways they disallow most other things, unless you want hefty fines.

I'm in Europe, and at least I can have little flowers within the grass, can plant any trees as long as they won't damage any buildings or cables, and otherwise I can customize my own garden. I could even plant vegetables if the dogs didn't stamp it, and wouldn't be so cheap and readily available in the supermarket it doesn't worth to look after them (once I did grew chili in pots since they're more scarce in the supermarket).

I have a small lot (0.2 acres) with a small lawn, my kids play on it all of the time. It's the only reason I haven't gotten rid of it all and replaced it with native species.

I mean, that's true in any case.

It really depends on the specific grass and underlying soils, as you say.

I'm the guy at the City making landscape architects and civil engineers comply with drainage and water quality regulations.

We live off the tears of developers.

Exactly. People love to treat it as "a war on cars/lawns/etc.", but it's really a war on everybody who doesn't want to be legally mandated to have those. All we're asking for is to end the legal mandates (zoning, parking minimums, setback requirements, etc.) and for those who wish to partake in those wasteful luxuries to pay their true price without public subsidy.

Just implement a Japanese solution