Most of the time when people say they have an unpopular opinion, it turns out it’s actually pretty popular.
Do you have some that’s really unpopular and most likely will get you downvoted?
This would only deter people who would otherwise plan a child. Those people tend to have fewer children in the first place and are more likely to take good care of them. I actually think the best approach to reducing the world’s population increase is a heavy investment in education including reproductive education, especially in poorer countries which are the ones still actually growing fast.