Fortunately, there are millions of buildings that remain standing as evidence of what was done in the past. So at least there's that!
And we can accommodate for 'selection bias'.
We have all of the historical evidence we could ever want for 'how things were built', basically 'infinity examples'.
I think some things were more robust, particularly some of the old framing, like in Europe, with non load-bearing walls etc. Those will stand for 1K years, but arguably unnecessary.
You have to get a representative sample, that's the tricky part.
So there's that!