Feedback may not be absolutely necessary in all disciplines (endeavors? arts? crafts?), but for some things it can be vital. I recently found out that discs in my lower back are closer together than they should be, and my spine is slightly out of alignment in two planes, probably because of bad posture (the day job) and incorrect form during high intensity workouts (which I need to even break a sweat). I'm thinking that getting a physical trainer or other specialist to critique my form would probably be a good idea, especially if I want to continue my workouts.
There are cases in which it may be ... very specific. You're looking for feedback from a select group / highly refined community. Though this also presents issues -- see discussions of "the problem with mathematics" where there might be a half-dozen people who are capable of even following, let alone assessing, an argument or theorem.
Where you're working in a system without any selection, you're not dealing with an evolutionary system (or you've misidentified the selection process).
In some fields, and at some levels of mastery, yes, feedback may not be necessary. If someone is truly at the top of their craft, pushing the bounds, with no superiors or peers, feedback could be destructive. I posit that most people aren't at this level, and those who think they are probably aren't. Even so, contemplation would probably be a good idea, but that's probably already happening in those cases anyway.
