By "have" kids do you mean: be the biological parent; finance materially; or spend time looking after? Because solutions start to appear if you separate these t

By "have" kids do you mean: be the biological parent; finance materially; or spend time looking after? Because solutions start to appear if you separate these things. For example, one thing to try would be (reverting to) a society where grandparents raise the kids. Then people can invest resources in kids when they're 40–70 instead of 20–35.