Birthrates are well below replacement almost everywhere except third world countries and Israel.
COVID has made things much worse.

Real economic growth is driven by increases in population. Young people have energy, create businesses build homes and consume a lot.

Civilisations that don't reproduce at sufficiently high rates die out quite quickly in historical terms.

The farcial profligate money printing, zero interest rates, QE etc has been an attempt to paper over this fundamental crisis.