Why though actually can't we build the way our ancestors did? Is that knowledge all lost? The Palace of Westminster isn't a farmhouse but it seems like a pretty beautiful, functional, durable building.
We can, but we prefer to use way cheaper and faster methods because before the "ancestral" building is finished, with our modern methods, we have built, used, torn down and rebuilt several times.
The Palace of Westminster rebuild took 30 years, but that was a pretty exceptional case. Balmoral Castle took 3 years. I don't know how long more modest housing took on those days but I'm assuming in the realm of a year. Even a few years to build a larger building seems acceptable if you get something reusable for much longer, and more timeless. Anyway, I think it's interesting to compare.
You'd think we ought to at least be able to build some monumental architecture some of the time, even if cost is prohibitive for ordinary buildings as the argument goes. It's simply impossible to my mind that we command more energy than our ancestors could dream of and yet it's somehow "too expensive" to ever achieve the kind of works they did by hand. There are obviously factors at play which have nothing to do with cost.
Because we stopped making buildings to create shelter, or livable places. The process became industrialized, and serves the same goal as most processes in a capitalist society: to generate most profit at minimum cost.
Even though today we build things with minimum cost, there's still not enough housing for everyone. There's a housing crisis in every major North American city, caused in large part by lack of affordable homes (and no, not everyone can work remotely from Quaint Townville, Wherever -- in fact, most can't).
It does not cost a million dollars to build a single detached house. Closer to a quarter million for materials and labour, give or take the cost of land. Profit for the seller is what makes up bulk of the cost. Profit margin for the builder. Decades of steady profit for the bank that sells and services the loan. The purpose of housing has become to be an investment vehicle, not shelter.
We could easily afford to build and maintain enough housing for everyone. Create and sustain vibrant communities where people's basic need of shelter are met. But it's just not compatible with the capitalist mindset.