There are better ways to build discipline than spending a huge chunk of ages 5-18 doing otherwise pointless busy work.

Completely agree with this. I used to skip most of my classes but would get As on all of my tests.

Now I struggle immensely on going through the every day grind of adult life.

That's why I don't do "real work" anymore. You understand not everyone has a goal of being a salaried employee in life, right?

Perhaps it's worth sampling the population and seeing whether outcomes match. I'll go first. I didn't do this. My parents intentionally did my cursive writing homework for me so I could read and go out and explore the countryside.

I now run eng at a prop trading firm that you'll occasionally see in the FT.

It was the arbitrariness of academic work that got to me. Real world work tends to be clearly directed at a goal, and if you acheive the goal it doesn't tend to matter much how you did it. Academic assessments (poorly designed ones, which happens to be most of them in my experience) expect you to do things exactly in a prescribed manner. Essentially 50% of what you're doing isn't actually useful learning, it's domain-specific learning where the domain is "what my professor happens to care about".

I wish you were wrong, but you're not. Ability to work a BS system absolutely is a marker of success in society.