A Stark Endgame
While demographic collapse is typically explored through an economic lens, the problem is far from purely economic.
Historically, people had lots of kids because it was the practical thing to do. A large family helped with business or at the very least resulted from a lack of access to birth control. Human advancements in labor and family planning have improved quality of life while yielding an unanticipated consequence: In a world in which it is “practical” from a self-interested perspective to stop after two kids (or have no kids at all) the only individuals still consistently producing children at well above repopulation rate are those with an ideological objective that supersedes self-interest (most of which society would consider ideological extremists) or those with an inclination toward authoritarian beliefs about how families and society should be structured (allowing people other than them to make decisions about family size). This would be fine if these inclinations were not laced with highly heritable components (and it turns out they are). This trend can be seen in the demographic data of every country, both between and within every religion and every culture.
Anyone who believes in science and data will see only one endgame. We are already well into this change. If you have ever wondered why different ideological factions in politics seem to be able to agree on less and less as time goes on, why they are becoming more authoritarian, and why tribalism seems to be increasing: You are witnessing the invisible hand of demographic collapse at work.
Population numbers will eventually rebound within a few hundred years, but progress the world has made in terms of women’s rights, freedom of speech, environmentalism, racial equality, gay rights, etc. runs the risk of systematic erasure if we fail to intervene.