To quote a wit somewhere (wish I could remember who, it really is a pithy turn of phrase)
"The future belongs to those who show up"
I fail to see why this surprises anyone in "the west" - we've spent almost 70 years turning mass infanticide into a public sacrament, Lo and behold, we now have a (allegedly inexplicable) shortage of children. Who woulda' thunk it?
It's not that simple though. People didn't just go "Welp, baby grinding machines go BRRRRR", it's been decades of extreme 'progress' to get where we are.
A bunch of creeps in power started whispering in everybody's ears
"Psst, do you need that fourth child? Get yourself a nice car!"
"Psst, do you need that third child? You might not be able to afford the mortgage"
"Psst, a second child is bad for the environment, lets not be selfish!"
and finally
"Why have kids at all? Have a fur-baby! All the kittens you want!"
Meanwhile these creeps then went "Oh dear we're out of babies! Better bring in their replacements! Oh you silly natives just aren't breeding enough for OUR needs, the line MUST ALWAYS GO UP"
Fit in feminism, birth control, and abortion in there as well and you just deliberately went out of your way to brainwash entire populations into genociding themselves by accident. That's still a crime.
So it's not just about infanticide, it's the entire concept of having children. Not to mention 'mysterious causes' making sperm counts plummet, modern men would be classified as 'almost sterile' by the standards of the 50's.