I go in more detail in my other comment but I would imagine this is a definition most people can't get behind.

> intelligence can be reasonably defined as "knowledge and skills to be successful in life, i.e. have higher-than-average income"

I think it just crumbles under light scrutiny. People have higher income for all kinds of observable reasons that don't have to do with intelligence. I have higher income than other employees at the same level just based on where I live.

Intelligence is something that is defined by academics. Surprise surprise that it it measures how people perform in a narrow set of academic skills.