Earlier quoted context omitted.
> as the population ages, who is going to buy all the McMansions? The McMansions will be unlivable by that point. They weren't built to last.
This is what people said about Levittown ( https://en.wikipedia.org/wiki/Levittown ), the archetype for postwar suburban housing developments in the USA. They did wear out, but the owners fixed them. If the housing is still needed, it will be maintained and repaired and improved.
Also, Levittown construction and materials are not comparable in any meaningful way to McMansions.