It's like that saying that it's not the fall that kills you, it's the sudden stop at the end. So, it's not declining population that endangers us, it's the sudd

It's like that saying that it's not the fall that kills you, it's the sudden stop at the end. So, it's not declining population that endangers us, it's the sudden drop in fertility rates that threatens us with a world of elderly people outbidding each other into utter destitution to get basic care from the few working-age people remaining. If the replacement rates do not drop to levels too low (~< 2.1), a new equilibrium will be eventually reached, but with a lot of trouble meanwhile. It doesn't help all the productivity gains from the last decades were mostly pocketed by the super-rich, instead of shared with the workforce.