I've been following this thread with great interest. As a relatively new amateur photographer who shoots primarily to memorialize my travel experiences, I think my perspective is probably a little different than a working pro who needs to consider the saleability of his/her images.
When I visit those locations that have been photographed a bazillion times by thousands of photographers imminently more skilled than I, my goal is primarily to attempt to emulate, if not actually replicate, those 'iconic images'. Sure, there might be hundreds or even thousands of almost identical shots out there, but mine are different and special because I took them. If I come away unsuccessful, I always feel like I have somehow done a disservice to the subject.
Granted, I have reached the stage where I would also like to be better at putting some of my own unique personality and perspective into my shots. But, as Roman points out, some of these places are so wondrous, that it is difficult not to be overwhelmed by them. When we went to Antarctica a couple of years ago, I was so awestruck by the beauty and serenity of my surroundings that I saw wonderful photographs every time I blinked my eyes. I added thousands of activations to my shutter count. When I returned home, I discovered that, with a few exceptions, all I had were a bunch of snapshots that did not capture the essence of the location or the feelings it inspired.
BTW, Douglas, your shots of the Zion, the Canyon and Mesa Arch have really set the bar high. Having stood in almost the exact same spots as you, I certainly did not do as well as you at capturing the essence of the location. Stunning work. Thanks!