Meanwhile, many legacy cities continue to lag

Pittsburgh.  AP ran a story, asking the question, "How does Pittsburgh have 20,000 vacant homes -- and a housing shortage?."  The reason for the large number of vacant properties is because more suburban housing was built than there was demand, hence housing abandonment in Pittsburgh.  

This is abetted by the fact that the Pittsburgh metropolitan area isn't growing all that much. The population has been stagnant since 2000, and shrunk some from 1990 to 2000.

Cities like Cleveland, Detroit, Baltimore, St. Louis etc. have the same problem.  Hence many vacant lots and abandoned buildings ("Vacancy: America’s Other Housing Crisis," Bloomberg).

From a filtering perspective, if you want to live in the city, there are plenty of options--e.g. houses that today cost over $600,000 could be bought in 2003 for under $125,000.  But if not enough people want to live in the city, the overhang of vacant properties remains.

Another point is how much demand is there really?  One example is a small developer, believing that the relatively low income Hill District "needed" more upscale housing to appeal to new market segments, hasn't been able to sell the houses ("Six new townhomes. Zero buyers. And one developer on the brink," Pittsburgh Post-Gazette). 

I think the headline of the AP story is misleading, because it doesn't discuss at all a housing shortage in Pittsburgh.

DC.  The market turned in favor of urban living--the federal employment engine was strong and grew further as a result of the government response to 9/11 and the need for improvements in security technology ("Understanding the DC housing market: demand for urban living, not the construction of new housing, is the driving force," 2021) and vacant housing was rehabilitated and occupied.

Only with the Trump Administration's recent destruction of the federal government, especially for jobs and agencies based in DC and the suburbs, has DC's housing market turned downward ("DOGE Is Dampening the DC Real Estate Market," Washingtonian).

Public Land banks.  But when they do want to live in the city, the properties need to be rehabilitated and the cost can be extremely high relative to costs of existing housing.  The AP article argues that Land Banks, public authorities that acquire and sell vacant properties, are a potential solution.  

Philadelphia.  Photo: Matt Rourke, AP.

But most move particularly slowly with many bureaucratic hurdles and are usually underfunded ("City Council grills Land Bank on selling only 1,017 vacant properties in over a decade," Philadelphia Inquirer).

In Detroit, the Land Bank there has more recently acted as a developer to get buildings in shape for sale or rent.  Some neighborhoods have done better than others, and so the Land Bank is criticized for differential effects ("Detroit's land bank says it has led a city housing revival. The jury is still out," Detroit News)

Nonprofits. Various nonprofits, in Detroit, Cleveland and elsewhere, also do this kind of property rehabilitation, sometimes with the aid of receivership statutes, providing the ability to clear confused titles and cancel outstanding liens.

Lesson: focus.  Most of the successful nonprofit efforts focus on particular neighborhoods, aiming to build a critical mass of improved housing, rather than take on a scattered site approach.  This is tough though politically, because everyone wants their neighborhoods to be improved.