If the general solution to career advancement is just to work more hours, we'll be a bunch of unhealthy, overworked burnouts.
Where's that expectation that you have to be best of the best coming from?
(Not to mention, the expectation to be seen and treated as the best of the best, without putting in the work.)
Sure you can put more hours into something to get better and improve your performance.
But why should you spent more hours on your free time? Some employers grant a free "afternoon" every-week for employees side projects. Guess what more side projects, less burnout...
Source: The company that support PostgreSQL for my workplace do that. Which we were doing the same.
People are going to have kids regardless. So, the question we're really asking is, should we structure things so that people have time to raise those kids that they are already going to have. I haven't reviewed the literature, but I'd guess kids who have their parents present in their life have better outcomes.
I am aware of hiring decisions between several candidates that hinged on their side projects (or lack thereof).
some workers like to spend time coding off-clock: that's fine.
some employers prefer those workers: that's fine too.
I'm not interested in being one of those workers, and quite happy to avoid those employers. I have no trouble finding workplaces that respect my time.
I think what we want to limit is employers pressuring people into side-projects as a form of unpaid overtime. Other than that, I'm not sure if I see the problem here - but I guess I'm a part of it too.
As a 20-something year old with no kids, I certainly do not feel any more entitled to "go far in my career" than anyone else, just because im dead inside and write code on the weekends after work. Anyone who thinks like this is an asshole who I don't want to work with.
In my experience, the people who have kids generally have more experience because they built up the experience before getting the kids.
Can you see how this presumption could be problematic?
Edit: fixed grammar
So, you have kids, great! Spend time with them, enjoy your life. Presumably you're a software engineer so you're making more money than the vast majority of the world. Enjoy that, but do you feel entitled to go as far in your career as someone who dedicates more of their life to their career? Should those people be punished by being displaced by someone like you who presumably has less expertise due to spending less time on your career? I'm not trying to put words in your mouth, but I'm struggling to understand why our current system should change to cater to your lifestyle choices of having kids.