The thing is if you know exactly what you are looking for, like in your example, or a QR code, or a barcode, it makes sense to tailor an algorithm. But you may not want to have to maintain a complex algorithm every time a small change happens (say new kind of ships appear). Or you might want a generic approach (recognise any objects, including objects that did not even exist at the time the code is written, but will appear in the data). In such case I can see ML being a good choice.