You make it sound far too easy. Alaba is extremely versatile and talented, he used to play as a CDM/CM, even as a winger and did well, then Heynckes decided to make an LB out of him and he's been even better there. He knows how to dribble, shoot, cross, take penalties (if you are defender and you are the designated PK taker in a team, which has players like Ribery, Robben and Mandzukic, you are really special), he's no traditional LB by no means. You could basically deploy him anywhere on the pitch and he would deliver.