Quick Claw is not a good item for competitive at all. It works randomly (and rarely), and there is no guarantee that it will be impactful if/when it activates. You can't base your decision-making on random chances, so Quick Claw plainly doesn't factor into your game most of the time.
In other words, you are never going to make a play that depends on Quick Claw working. On the other hand, you can always trust an item like Choice Scarf to hit a speed benchmark or Life Orb to secure an OHKO. You want items with a consistent, dependable and useful effect. Quick Claw is an unpredictable luck item.