No, you misunderstood completely. Under the OP’s proposal, you have people raising their grandkids, not their kids.

So if I understand: Starting today, a pair of 20-somethings has kids, hands them off to their parents to raise - OK, their parents had experience now they are doing double-duty, but they know what they're doing raising kids.

Now... 20 years later, those children have kids and hand them off to their biological parents who ... have no experience raising children. Also, which grandparents? Mom's or dad's?

Ask the OP, I wasn’t the one who suggested the idea.