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.

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

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