> UPDATE: There are, by and large, two broad types of writers: extroverts who promote themselves capably, but might or might not have equally good skills, and introverts who lock themselves away and aren't great at self-promotion.

That in itself is a broad swath of a statement, and not necessarily true.

Why does being an extrovert have to be correlated with being and impostor, and introvert just simply these poor humble victims whose talents are overlooked?

What I saying is, if you're looking for work - applying for jobs is never the time to be humble. And if you are already confident, being humble won't help you.