The thing about engineer being a good teammate: I don't think it is about extroversion as much as realizing that modern software systems are very non-monolithic and thus require cooperation among many different services to work effectively. This means that the days when a person could write the entire thing by himself/herself is over, and a lot more co-operation is required among engineers to design and build effective systems. That cooperation requires a certain amount of communication skills (apart from stellar technical skills), but it doesn't mean that you have to be an extrovert.