Birth rates decline pretty proportionally to economic development, arriving at well below replacement levels in highly developed countries. In light of this, it seems misguided to expend energy personally convincing people to have less children, when we could just focus on bringing more people up to the western standard of living that, apparently, organically makes having many kids mostly unappealing.

Less charitably, this is the kind of advice that mostly seems like an excuse to preach at people.