Your Amazon Associates report has three numbers that look similar and mean very different things.
Clicks measure interest — how many people your pins actually sent to Amazon. Low clicks usually means a pin or targeting problem, not a product problem.
Ordered items measure conversion — how many of those clicks turned into a purchase (of anything, within the window). This is where product choice shows up.
Shipped items measure what you'll actually be paid on, after returns and cancellations. It's the number that becomes commission.
Track conversion rate — ordered items divided by clicks — per product. A product with fewer clicks but a much higher conversion rate is often the better use of your time.