I get what you are saying Mike. And yes, the routing isn't a feature of the golf course, it is the golf course (you don't say the number one feature of a car is the car).
That said, as a differentiating factor, I'd still place it behind greens, drainage, and contour. On the other hand, bunkering is much "lighter in weight" than those things, while being more visible. It's super important still, even if it isn't number 1.
But the visibility part is important. Stand on the tee of a hole with at least one bunker with visible sand in it and squint until you can barely see. The only discernable feature will probably be the whitish beige of the sand among a sea of green and greenish brown.