What's wrong with many images made by people who aren't very cautious isn't really that they're overcooked, although that's a problem, or that they're too heavily vignetted, or that they have HDR applied, although these are also problems. No, the problem is that the viewer can see what the photographer did. The choices the photographer made are extremely present in the frame, the photographer's idea(s) are altogether too front and center.
I don't wish to state a rule that every choice the photographer makes should be invisible, for that would be a bad rule. Some outstanding images have been made which are primarily about the photographer's choices.
The point I wish to make is that if your choices are obvious to the viewer, you run the risk that your image will be about you and the choices you have made, not about the subject and the meaning you wish to convey. You, the photographer, now stand between the viewer and the image. You can see it every second of the day on flickr, the comment is not "what a great truck" it's "what a great HDR."
I vignette everything. Well, not snapshots thrown up in bulk for the family, but any image I am presenting as My Work. I do this from habit, because it's what I was taught at some point a long long time ago, and because it does close up the edges of the frame visually, strengthening what's in the frame. The important thing here is that I vignette below the level of perception. When you take my vignette away, you can tell that it's gone, but you don't notice it when it's present -- at any rate you don't if I have done it correctly. The point here is that I process, I process images quite heavily, but I strive to make my processing choices largely invisible.