I have known, have met, and have worked with, many people who have "lots of education", but:
-They cheated in most of their classes, and don't actually know anything about the subject.
-They did well on the theory in a classroom, but can't actually use or apply it practically in the real world.
-They selected an overly niche degree with limited utility and opportunity.
-They received all of their education from non-accredited institutions who basically exchanged money for a diploma.
-They're technically good at what they do, but they're too irresponsible to be trusted to do it.
-They're technically good at what they do, but they're too lazy to do anything with it.
-They're technically good at what they do, but they have a bad attitude and most places don't want to hire them.
-They're technically good at what they do, but there's no market for those job skills where they live.
Usually it boils down to either "They're not actually good at their chosen field", or "Even if they are good at their chosen field, they're not actually good at the job", with the occasional "you picked the wrong field" mixed in.