> Gaps in supply chains and power failures would lead to millions (or billions) dying of starvation, dehydration, or exposure because they don’t know how to provide for themselves. People who’ve studied and practiced survival skills (or who retained that knowledge in physical media like a book) would survive.

Hahaha, bless. I'm one of those people, I hunt, so I spend a lot of time out in the wilderness.

And if civilisation suddenly collapsed? My hunting and survival skills aren't going to do shit when I'm surrounded by thousands of other people who are competing for the same limited pool of resources. I might be able to identify the signs that a deer has browsed here recently, but so can many other people, and when we all turn up in the same forest looking for food en masse, well there's only so many deer a given area can support.

> Drop someone from humanity’s hunter-gatherer days into the same situation and they’d have a better chance of surviving than most contemporary humans.

Unfortunately, as the contemporary humans will likely resort to banditry to supplement their survival chances, your idealized hunter-gatherers are doomed to being stood over at best, murderered at worst.