>>Then you charge 5x the normal rate of a salaried engineer, work normal hours, and start accumulating real assets.

This is dream which happens only when you are asleep. In real life an older person is less energetic, less enthusiastic, can't do weekends, has health issues, has responsibilities, has family commitments etc etc.

Young people work insane hours, they do that for cheap, they show up on weekends and are more flexible in general.

In most cases. Like in everyday cases experience doesn't pay well as you think. Even in professions like medicine and law that is true.

The assumption that experienced people get paid well applies for a minority few people who for nearly all practical purposes are an exception to the whole rule.