Explainable, they suffer from depopulation so culture adjusts to make it as easy as possible for people to have children. Still doesn't help.

It’s not a matter of depopulation, it’s always been in the culture

Depopulation isn't necessarily suffering

Doesnt it require rejiggering existing societal strcutures tho? Like everythings seemingly built on infinite growth

if everything is built on the premise of infinite growth, then eventually everything will fail