Useless mouths? Christ.

Yes, some cohorts are more useful than others for nation building, that's just reality, especially if excess mouths are net drains relative to national resource available. Too much excess and not just useless but actively detrimental to development. It's not saying time to purge, but excess demographics can dilute development resources too thin, double bad if above domestic carry capacity, i.e. getting import dependant trapped.

PRC averted 200-300m birth who would have spread family resources into developing country trap. The family planning exchange is non-existing 400m low skilled workers / subsistent farmers that is net drain on national power vs having 100m tertiary to uplift into developed country. All PRC rising in the last 20 years is because PRC family planning aborted a fuckload of 2nd/3rd/4th+ siblings so families can concentrate resources to get 1st kid into STEM. They speedrun the high skill human capita game, compressing 100s of years of human capita accumulation in 50. There's downsides, but they come after the up.

What's better for development, a 1.8B country of 6 Nigeria's and 2 Japans or 1.4B country of 2 Nigerias and 6 Japans. The latter. And you would recognize the former, while all lives are special blah blah blah is absolute developing shitshow. Every Nigeria PRC avoids is 200m of less governance overhead, i.e. make work jobs. AKA see which way India trended. Look at new gen of PRC protein consumption and average height vs alternative, stunted growth from malnutrition that literally makes significant % of population too stupid to integrate into modern economy. That's what happens, you can literally fuck up your human capita stock so much by diffusing limited resources that 100s of million become too biologically stupid to do modern jobs i.e. even in PRC, 100s of millions from old times too stunted and innumerate to do even basic factory work. PRC didn't abort enough.