Buildings don't get taken down because 'they were built poorly', it's cheaper to rebuild than refurbish.

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.