Lazy and unmotivated are about his internal state, which you correctly point out we don't know. Lack of direction and ambition are observations of exterior actions. He is not moving in a direction, so we can say he lacks direction. He doesn't seek to be great or even good at anything so he lacks ambition. In making those two observations we have not ascribed any reason why he lacks ambition or direction. So complaining about people not knowing his motivations when we are talking about his actions not his motivations, is in fact a straw man.
Ambition is a personality trait, just like laziness and motivation. Your definition of the word is hella nonstandard. You can have internal ambition without there being a noticeable external effect, due to things like lack of opportunity, poor health, children, ignorance about what opportunities are present, and so on and so forth.
