It’s true that tour pros often align their feet left of the target. An open stance makes it easier to clear the hips, generating tremendous lower-body drive and power. Many amateurs take an open stance as well, but they typically do so not to obtain power, but to try to make the ball go left. Most amateurs slice.
Pros don’t slice with an open stance because their shoulders remain square. Oftentimes an amateur feels “closed” with square shoulders (particularly if their stance is open). Shoulders can also open up when you take that “one last look” down the fairway in your preshot routine.
Check your shoulder alignment in the mirror. For righties, you shouldn’t see your right shoulder at all – it should be behind (and slightly lower than) your left shoulder.