Take a look at your average individual from 100 or so years ago: probably working a manual job, lived through a depression and world war. Life was certainly harder for most in many basic ways. Obviously not true for all, but generally speaking quality of life has improved a lot.

Our culture is light years away from that in terms of the resilience that's generally expected from people.

Yes, I think it's fair to question the assumption that willpower has not changed.