Sure, people should indeed become "sorta good" at multiple skills. In practice, they do. Many people know how to doodle or play charades or tell stories or sing sea-shanties. Otherwise, hobbyist Cessna pilots would not exist -- nor the word "hobby". In real life, statements like "he is even unable to entertain himself" are pretty false.

> the vast majority of real life is not D-Day or crash landing in the Hudson

Sure, but a significant portion of life is spent interacting with the results of other people's work. When you get into a car, would you rather that its microcontrollers were programmed by someone who

A: Felt continually distressed and defeated that he had not thoroughly mastered sailing, animal husbandry, military history, rhetoric, first aid, copy-editing, painting, masonry, carpentry, and several other skills.

B: Felt fulfilled that the only domains in which he had deep knowledge were microcontroller programming, cooking seafood to his wife's taste, and the emotional/medical meanings of their child's sounds -- yet that they had merely a hobbyists' knowledge of hiking, sketching, kites, anime, and the history of flight.

Because I'd rather a world with more of B and less of A.