> I think most great parents didn't feel ready

What makes a great parent?

Providing food, clothes, health and shelter? My parents weren't ready. I interrupted my fathers dream he was on track for, but only later learned about by doing the math in his rare moments of nostalgia after a cancer diagnosis and given a handful of years to live. My parents did a hard pivot and worked 3-5 jobs between them at any given time to make ends meet because his sense of duty to the family he wasn't ready for. I rarely saw or interacted with them, but gained valuable experience in navigating the world independently and being responsible for myself. I had good parents -- I was fed, clothed, housed and healthy enough to make it to adulthood and move out on my own after high school.

This part stuck out:

There are good reasons to wait, [...] My children have not had to live with parents who are working 15-hour days, the way we worked in our 20s, or who are financially desperate, as we might have been if we’d been paying for children on the salaries of our 20s. Our professional standing allows us to skip work for pediatric appointments or parent-teacher conferences. [...] I got a promotion [...] when it was time to buy a piano. We all sit down together for home-cooked meals most evenings and talk about things.

That must be nice, but I wouldn't know. My youngest sibling does though, their grandchildren knew that with them when they were younger too. My parents finally built up the stability that gave them time -- as I was on my way out. I have no idea who they are, nor they me, that was not our relationship -- I had that with my grandfather, but only briefly. And I would not trade that decade for anything in the world, except maybe to have had that with my parents, even if only for a few years to get to know as a child should. My youngest sibling got the great parents because they were ready to be by that time.

You get to be a great parent because you can spend time with your kids -- whether you "felt" ready or not you were, but maybe consider that's because the time you waited gave you the time to spend with them. You're looking at it in terms of maximizing years. Having more years doesn't mean anything if they can't be quality years.