8-12 years of child rearing is very expensive. That's without even taking into compounding returns from working longer hours, seniority, experience, and investments.
To make the point clear: children raised by young and growing parents and different from children raised by old and established parents. Slow startups are different from fast startups. No judgement, they are just different. But the premise that a fast startup is the only way to do a startup is false. It's just choices for different outcomes.
My parents have not come close to being financially recovered relative to later-parents a decade after we've all left the house. The delay you are talking about compounds to absolutely massive differences in my experience. Trying to multi-task both the other "life" check boxes and your work is going to have large hidden costs on work because of these compounding advantages.