I think it's more about concern for society and Western civilization in particular. Low fertility will cause nations, and cultures, to contract and eventually collapse. 'Eventually' not being some excessively distant reference - South Korea may well become a failed state within our lifetimes if nothing radically changes, seouly due to fertility. And most other nations will be right behind them.

As for anybody's parenting - I have certainly raised my children in ways that would offend the sensibilities of this group or that. But it's what I think is right. So under this mindset, and a bit of the Golden Rule, I do not criticize other's parenting outside of obvious extremes.