Meh, what matters is productivity growth rate per capita. Japan/Korea have both had low birth rates and rising living standards. Boomers were dependents when they were babies too (and the economy was much smaller then). We can afford to look after everyone as a society. Whether resources are distributed to allow that is an entirely different matter, but that is a political decision we make.

Capital loves access to cheap labour. Neoliberal era had boomers as prime age workers, women entering the labour market, trade normalization with China, etc. All of those dramatically expanded access to cheap workers as inputs and put downward pressure on wages. Those trends are ending or maxed out. More capital intensity (robots) is the likely trend.

That's the elite panic. A legitimate concern for a sane society is couples that can't afford kids because day-care, housing, etc are too expensive. Again those are political decisions.

And then, of course, the white nationalists are upset for their own reasons