Do you have any experience with timber frame construction? (most architects don't) Timber framing is inherently modular, often fabricated off-site, and usually erected in a day. Panel enclosures (high thermal efficiency) are an industry norm.

There's a lot of gee-whiz thinking out there amongst tech-minded people about how CNC machining, 3-D printing, and robotics are going to revolutionize building. Most of them have never built anything.

The boots-on-the-ground reality is that building smaller houses hasn't been of much concern to "Architecture" (not enough money in small houses), plus the building market is beholden to multiple sub-contract processes, each of which is an economy of scale in itself that can totally wreck your critical path.

The human element (craftsmanship yes, but also processes that are human scale) is mostly left out of the scenario you're describing. What do you propose that we do with all the "labor" that will be displaced by these "improvements"?

And, yes, we should be building smaller, more efficient houses. We don't really need machines to do that. What we really need is a banking system that invests in people, not corporations.