That doesn't seem workable.
The suburbs take a huge amount of land. If everyone lived in NYC-level of density, we could all fit in New Jersey. If we all lived in middle-missing housing level density, that amount of land is still far less than the total area of all the suburbs.
Upzoning does not mean you automatically get a building at maximum allowed density, it means you increase what is allowed and let the market decide what makes sense where. It would play out exactly as you describe.
Music. Street racing. 24/7 dog barking. Density is hell.
Sure it’s not like living next to Times Square but it’s far noisier than a neighborhood of single family homes.
That and the crushing car dependency.
But a lot of people like it, so hey, good for them too!
To each his/her own.
If it were legal to build low-rise, medium-density housing throughout the cities, more people would choose to live there, rather than the suburbs, because commuting sucks and city amenities are great.
Instead, restrictive zoning codes set aside large swaths of the city for single-family homes; the large plots of land they occupy mean that only rich people can afford them, which forces everyone else to compete for a limited number of apartments. Land for apartments being artificially limited means that construction cannot keep up with demand, so apartment prices rise too. The working class get forced out to the suburbs; eventually the middle-class have to go, too, whether they like it or not.
We should repeal these zoning codes and let people build dense housing wherever it's economically justified. Then, the choice really could be "to each his/her own": people who genuinely prefer to live in the suburbs could still go there, while people who would rather live in the city could do that instead.
We have suburbs because people want them.
The best example is when I lived in Singapore. Great public transit and high density housing. No need for a car.
When I talked to Singaporeans, most dreamed of owning a single family home (a landed home) with its own yard and a car. And we’re talking 90% preference.
When we all have windows open in summer we can hear one of our neighbors' TVs a bit though, and there can be noise between floors of multifamilies.
I’d assume one needs a bit broader set of data than that that comes from a clearly anti-suburb position.
It’s like only looking at NRA sources on the need for gun control.
The gist is that we've funded the construction of our infrastructure nationwide without accounting for the cost of maintenance. Now after decades of neglect, the cost of fixing all of our infrastructure is astronomical, far worse than if we had been doing it correctly from the beginning.
[1] https://www.strongtowns.org/the-growth-ponzi-scheme
[2] https://infrastructurereportcard.org/