In an adjacent thread, there was a good response from the point of view of an old-fashioned clothes wearer:
Their bottom line was that modern materials deal with being wet much much better, and can last longer (especially around hungry bugs/animals) but furs can be pretty warm and reasonably light.
I’d add that modern wicking underlayers are also a big improvement. Before 1970, a major skill of mountaineers was pacing oneself so that sweat never accumulated on ones clothes (which would make them either non-insulating, or very hard to dry). Nowadays, don’t need to worry about that nearly as much.