I think older people who have more patience are supposed to help. We moved to America when we were young so my mom had raise my brother and I by herself, which was very hard coming from somewhere people live in multi-generational households. She had very little patience for it. But she and my dad have way more patience for my kids. My mom lived with us for a year and then my wife’s mom lived with us for a year while our youngest was 2-3. Then we moved 10 minutes from my parents. My middle child kept getting ear infections so he went to my parents’ house every day for two years. These days my boys (4 and 7) go to my parents’ house every weekend.
I don’t think younger people are wired to be taking care of babies full time. I’d imagine in nature they’d be out hunting or gathering and our attention spans are wired for doing that.