There are also plenty of multiplex designs that have good noise insulation.

In reality people do want to live in them which is why zoning laws are used to prevent them from being built. If people refused to live there, there would be no need for zoning as developers wouldn’t build homes people don’t live in.

You would have each unit certified as either A, B or C. C being nearly no noise insulation, A being very quiet.

Let the market decide what they want to pay for.

As if construction costs were the primary factor in determining the cost of real estate in places with housing crisis problems (like the Bay Area).

Of course, then you’d ask, well why are construction costs so high in the Bay Area? And you might hear something about earthquakes, insulation, whatever. But the real reason is that contractors and construction workers need to live here too, and living here is damn expensive!

You're making an assumption that noise insulation is particularly subject to the market. Unfortunately noise 'insulation' like other insulation is extremely sensitive to competence in instiallation and maintenance.

Because it isn't particularly easy to gauge when shopping I don't believe that it is... and in markets where there are more prospective renters than units, it especially isn't.

And for some people, it beats a 3 hour commute. People should be free to choose what they prefer as long as it's safe.

And since housing is a zero sum game the market is already rigged in favor of landlords. People generally don't have as much choice where to live when you start considering school access, public transit, commute and so forth. Relying on the market to solve housing will simply result in miniature SFs popping up over the US, just like what's happening to Austin.