Cultural traditions were vanishing, but not because of some inability to keep up with progress. When Curtis was visiting the reservations in the early 1900s, indigenous people were being forcibly assimilated by the American federal government after decades of violent eradication and seizure of land.
I think its so horrible how many lives the US has obliterated, there was absolutely no reason (other than disgusting white pride, and greed) for the US to rip apart innocent peoples lives and cultures