How NIMBYs view the world

major upgrades will need to be done every 20-30 years

That is true of almost all building methods. Go to Gary Indiana or Detroit and you will see all the top end housing that didn't last long without major maintenance.

frame on top of poured concrete buildings

So all the frame on slab apartments from the 1950's/60's that are 2-3 stories and "lasting" just fine 50+ years later, that were built the same way seem to prove you wrong.

I work in commercial insurance

You seem to be confusing insurability vs actual material/maintenance requirements to keep a structure in service.

They degrade

So do the concrete and steel, Thus the one on Wilson street that now requires demolition due to the owner not doing proper maintenance.

….and with it rents sink, they stop being “affordable housing” and become compact government assisted housing….

Hah, what a load of BS. That only happens in "dying" cities, in growing cities they get torn down and rebuilt (normally at a higher density). That is literally every "new" property built inside the belt-line in the last 15 years. Degrading structures in a high demand area, so the old buildings once they can't support the desired rent get torn down and new luxury stuff put up.

especially in areas that the land doesn’t have enough inherent value

That no longer exists inside the city limits. Madison has minimal land to develop or annex to allow for future growth of the population. It is landlocked by lakes, surrounding cities, etc.

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