There's been a rash of people like Elon Musk posting rants about "declining birth rates in the developing world" (and sometimes dog whistling while at it) - getting upset that contrary to the worries of Malthus and Ehrlich, it turns out humans are not the same as bacteria in a petri dish just exponentially reproducing until they exhaust all the carrying capacity of their environment. Instead, it seems that those of us that are in paradigms where we have relatively high per capita energy and materials consumption, respond to economic, cultural and environmental stimuli, and slow our roll once we feel we are at an "x" threshold of population density and environmental & economic stress.

Given that we live on a finite planet with finite resources this small bit of self control might just be what saves humanity from a truly dystopian future.

What the demographic shift of less younger workers versus more retiring seniors does mean is that our systems of depending on constant growth of consumption for our faith in our currency and financial institutions, and for providing for government guaranteed retirement funding, both end up under threat - but those issues could still be easily fixed simply by allowing more immigration from the multitude of places on this globe that still have relatively high birth rates, that have plenty of people with strong work ethics seeking greater opportunities.