>houses will simply fall into disrepair, as nobody will be able to afford the costs of fixing them as they age

That has been true of mansions for hundreds if not thousands of years ;)

My opinion is that the author is totally off the mark due to conflating two separate aspects of modern home building.

I’ll use these definitions in order to decouple the two aspects.

McMansions are custom homes built by the nouveau rich. They can be in greenfield developments or as teardowns in established neighborhoods.

Spec ("speculative") homes are houses built as a collection by a developer and then sold to their owners. There is usually an HOA.

A McMansion can be built poorly for sure. But more frequently it is built with a "most home for the least cost" mentality. The materials and quality are high but there's something missing. I think what's missing is craftsmanship and architectural finesse.

Spec houses can be built well and may are. But like McMansions - the dominant philosophy is "most home for the least cost". Those that are not built well - and that's is likely the majority - will result in large, unexpected repair costs for future owners.

McMansions and spec houses usually occupy mutually exclusive developments - which make sense since someone building a custom home doesn't want to be next door to a spec house.

A McMansion is only slightly more likely to avoid the "something is missing" aspect of large modern spec houses. And it's from the same root cause - a lack of craftsmanship and architectural finesse. Where I lived until recently and for over twenty years, there were several houses torn down and replace with McMansions. The one beside me was originally a small (~1200 sq ft) brick ranch like mine. It was replaced by a McMansion. The owner/builder told me directly that she builds "the most home for the least cost". She lives in them for three years and then moves and repeats. The one across the street replaced a very charming stone house in the Tutor style. I was sad to see it go. Its replacement was a house that occupies most of the lot - a 3/4 acre lot - but I do include all the ugly "hard" landscaping as occupying the lot. The lot had looked so large and beautiful with the small stone house. Both McMansion were built by the same builder. Neither had an architect (structure or landscape) involved - and it shows.

Another example on my street was truly a head-scratcher. The owners tore down a really nice 3000 sq ft brick house, and replace it with a really ugly 4000 sq ft house of much lower quality design and materials.

I get that the standard use of "McMansion" does encompass both types of building, but I have long distinguished McMansions as those that are custom-built. If someone else builds and then sell you a house, It’s no kind of mansion – it just a large spec house.

I have little experience with spec developments. I've no reason to venture into such exurb wastelands and thankfully all of my friends share that opinion and don't buy them. I assume they exist here - but they are dozens of miles from the city.

I live in a charming and affordable neighborhood that is a 15 minute drive to downtown (with light rail connections too). The houses were built in several generations from the 1920s to the 1970s. The schools consistently rate among the best in the state. McMansions are exceedingly rare here. Houses are rarely cheap and are of high quality. Lots are small and zoning doesn't allow for much of an increase in footprint. Even if it did, it would make no economic or aesthetic sense to tear one down. It does make sense to fix one up.