You have significantly over-estimated the procreational success rate of men. Consider this research[1] - in the ancient past, the rate of long-term descendants was seventeen women to one man. Note that this is about long-term, multi-generational success, so the rate was higher in each single generation.
[1] https://psmag.com/environment/17-to-1-reproductive-success
Re:Explaining Sex Rate Changes
by antisthenes on Monday April 08, 2019 @04:24PM
(#19608678)
Yes, in the ancient past.
If you read my post carefully, you'll see I only estimated the percentage for societies where monogamy is enforced (either through peer pressure, religion, or both)
I also did not cite the source you did, because I consider it of enough poor quality to be unreliable in debate.
In a monogamous society that has roughly equal men and women, everyone has the opportunity to reproduce. We're talking about a specific demographic that is struggling. In other words, those 18-29 men not having sex now (probably) will when they become 30-35. By that age most people are settling down into monogamy. And those men will be (probably) be in a better economic situation and therefore more desirable as mates.
Even in western cultures where monogamy was pretty strictly enforced by the church and society, I doubt that more than 80% of men procreated (wish I could cite sources, but there doesn't seem to be good data about this)
We also need to do away with the stigma that you can't have a fulfilling, productive and contributive life without children.