I agree this is a legitimate possibility. The developed world is all declining when you exclude immigration, and the whole human population should peak in the next 20 years.

The Fermi paradox assumes the pre industrialized human history of a person averavjng around 7 children. As we ended many causes of early death over the past century, the population exploded. Then increasing contraception availability, education and career ambition led to a higher opportunity cost of having children. Now financial constraint is keeping many from deciding to.

It’s reasonable that past 2100 the human population is significantly less than it is now, and continued economic growth eliminates resource scarcity. We won’t have any need to grow to a K1 civilization beyond insane levels of resource abundance and computing power per person.

I think we may start growing again if/when financial constraints or the need to work don’t impact people’s decision to have children.