This is like saying

"it could just be that people who are successful happen to be hard-working, not that working hard increases your chances of success"

The societal level of denial has reached new heights indeed.

On the last point, i am not even sure there is correlation let alone causation. Successful people i know hardly work a lot (or they do but in short extreme stunts, like 3 weeks of 80-100 hours a week and then almost idle at 0-10 hours a week for the next 6 months). They mostly just tuned themselves into ability to get "into right place at the right time" at a rate way more frequent than regular folks, by having and consciously developing right personality traits.

> by having and consciously developing right personality traits.

Which takes a lot of effort and hard work.

> They mostly just tuned themselves into ability to get "into right place at the right time"

Which takes a lot of hard work

> then almost idle at 0-10 hours a week for the next 6 months

You have been tricked into thinking so, they just work so much more efficiently at some point and delegate a lot - at which point they are already successful due to their previous hard work

Except you haven't actually given any evidence that kids cause happiness, just a correlation.