Yes, houses got better because materials got better. Windows are better. But the construction of the houses is worse.

The precision of how the wood or material meets is worse (when cut at the site). There is a huge amount of sloppy work in modern construction.

No, the construction of houses is not 'worse'.

There was a ton of horrible practices in the past.

The 'sloppyness' of the worker is mostly a separate thing.

Yes - they can do crazy things, but that's not a function of the better tools and materials they have.

I'm interested in how one would prove that one way or another.

It seems to me that in the past there probably was lots of shoddy workmanship and just no-one paid attention to it.

But I have no proof of that.

this is not true in my experience. prefab kits of all sizes (from sheds to houses to barns, like were once possible to order from a Sears catalog) have worse tolerances than a carpenter working on site. you can measure 3 times and cut perfectly, and still end up with a few mm gap (or sometimes worse) after tiny errors accumulate as you assemble piece after piece. it _requires_ measuring as you go and cutting on site to handle this small amount of drift and to really produce something of high quality. it doesn't come in a box