I subscribe to Hanson’s substack, and I also do not understand Hanson’s repeated exhortations that cultural drift is a severe threat. Indeed, I found the current article from googling to understand Hanson, ha ha. I agree with your summary of Hanson’s views. I don’t understand the same things that you don’t understand.
My own views (of course Hanson would disagree with these): Fertility decline will not proceed to the point that the Amish and Mennonites will dominate in 2 centuries. Why: a lot of things can happen in 50-100 years.
Some possibilities:
Amish and Mennonites, if they continue to grow in size, will not stay static. They may change and rediscover liberal values; those liberal groups will split off and form the majority population, replicating the structure we have today.
Climate change will decimate the global population, putting humanity into a problem-solving space that is hard to anticipate now.
Global population may decline for a while, but this won’t lead to a lack of innovation.
Global population may decline and eventually stabilize at a sustainable level. Why: People like having children. Status goals in wealthy countries mean that people are putting off childrearing, but that will eventually smooth itself out. People will start having something like replacement level of children.
What is the street address in Cambridge for the food court?