I am traveling in Europe for my lumber business and to refresh my German I am?? re-reading Lernen by Manfred Spitzer. This is a great book about learning and the brain, also available in English.
Spitzer points out that introverts are able to stimulate themselves to learn while extroverts require external stimulus. It sort of made me think of language learning with a focus on input. People who have interests, and follow these interests in another language, can acquire a great vocabulary and familiarity with another language without actually interacting with native speakers, until a later stage. This can be an advantage. At first the extroverts win out, because they want to use the language more, but introverts may be the eventual winners, in a tortoise and the hare race.
Perhaps a bit of both is best.