I like the OP, very honest.

Here's my 2 cents: In life, like in economy, everything's about marginal utility. If you work 5 days a week and you reduce by one, you gain 50% (free/family/hobby) time, while reducing 20% of work time. In the lost 20% work time, would you have produced the corresponding amount of output? Or are you even more productive because you avoid unnecessary meetings etc.?

It's clear that being an involved parents doesn't allow you pulling all nighters all the time or work through weekends and doing additional sideprojects. Though I agree that without full involvement and ambition one will not achieve a top position or become a tennis superstar, I think a good mixture of all aspects (family/work/sports/friendships) makes everything much more worthwhile. And in my opinion, all involved parent parts should have their fair share of those aspects.

- Parent with partner both working part time, living in a country that allows for that, equally sharing child care for two that regularly make them crazy, but it's soo worth it.