One of the major points, afaik, is that these beautiful buildings require a lot more manual work. It used to be that materials were expensive and labor cheap, but that equation reversed, and skilled labor required for such a nice facade now comes with a heavy price.
But I have no expertise in construction nor history so can't say if that's true.
Yes, that's true, but the style also changed so dramatically, not just means of production. e.g. machine production does not have to mean that overall building proportions became so weirdly unattractive as well.
But really, just because it was _cheap_ an _easy_ for a machine, therefore it meant it was _aspirational_, _desirable_ for a human. That is the core shift, it was primarily ideological (and we rationalized this new mindset _after_ it already reified itself).
But I have no expertise in construction nor history so can't say if that's true.