> A building from today looks much, much worse than let's say a building from even 300 years back
You don’t even have to go back that far. They still knew how to build decent buildings just 80-90 years ago. I think it all kinda changed after the Second World War. Maybe they needed to conserve money and build as much as possible?
I'm not sure how accurate it was in its argument for causality, but I recently saw a video arguing that architecture worsened from the invention of caulk for building sealant. With the ability to fill all gaps easily, buildings no longer needed to be designed and built with overlapping layers to prevent water and other elements getting in. This significantly reduced complexity and led to very simplified buildings.
The argument is that pre-caulk, the aestetics of a building came in pert due to design requirements. Those designs requirements disappeared post-caulk, as you can just fill gaps between any 2 panes with caulk. And with all things, we seem to regress to the lowest common denominator.