Seems to me that a photograph is like an ambassador, representing the thing or the idea that the photograph is about. Said representative can mumble and shuffle his feet, lie to the listener, not know his facts or refuse to be helpful. The print represents the idea in a somewhat similar way.
You might say that an image is about this particular piece of rust, but in fact it stands representative of all pieces of rust and more specifically the best pieces of rust, the rust that is really interesting in shape or colour, in composition, uniqueness and in it's surround.
If you photograph a winding path in the woods, it stands in for all winding paths and if it isn't twisting enough, or if the view is blocked by an unfortunate placing of a tree, or if there are distracting elements in the image, then it can't do a good job representing all winding paths. Oh sure, it can act as a representative of one particular path, and for someone contemplating hiking down it, they might want to see it, but for those enjoying the image, it isn't enough to represent only the one path. it needs to be the path of all paths, a path so well lit and presented that it makes a connection with lots of viewers.
Just because you take the best possible picture of a particular gorge, it doesn't necessarily mean you have the archetype image of a gorge - this one simply may be lacking, at least at the time that you photographed it.
Sometimes representing 'what it is' isn't good enough. The image needs to work in a different plane. I remember a Paul Caponigro image of an apple and it reminded me of an astronomical picture - stars, galaxies and clusters. The rust may not be the most famous, dramatic, wonderful rust around, but if it looks like John Lennon, then it's going to become famous. If it looks like Aunt Ruth, on a bad day, well maybe not.
What does this mean in choosing what to photograph? It means that we should be asking ourselves whether this particular scene from this position at this time, is capable of making an image which will stand representative of all similar scenes. If it can't - if you know you have seen better, and can't improve this one, then just maybe it isn't worth photographing, no matter how well you composed and exposed.
Mind you, if you are insecure, you could decide that none of your possible images is that good and so you don't take any pictures and end the day frustrated. If you know it's the best you can do and if the subject matter and it's presentation are the best you can find, then you have done all you can and since none of us can predict 100% the effectiveness of an image beforehand, why not shoot it anyway. In fact, usually the shooting is the fast part of the whole process. I'm just glad I'm not responsible for an 8X20 sheet of film (one of only a dozen I carry for an entire day's shooting).