I agree with you that this is going around in circles. Some of your comments on the thread (especially early) were overly simplistic regarding transfer between programs, and this has mellowed as the thread has progressed, and people may be reacting to those early comments. Extrapolating your comments from this thread to impugn your clinical skills is unreasonable IMHO.
Can residents transfer between programs? Yes, it's possible. But it's relatively uncommon. Most of the time it's for some social or other reason. Not uncommonly, this may involve a transfer to a "worse" program although assessing program quality is complicated / eye of the beholder.
Why is it difficult to transfer? Because residency training is relatively linear (PGY-1's become PGY-2s, etc), it takes someone dropping out of a program, or a program increasing in size, to make room. That doesn't happen all that often. Residencies also have a curriculum -- and starting in a program "mid stream" can be very complicated for the resident and the program.
Do I need to tell my PD? There's no law that requires this. However, most PD's are going to be looking for an assessment from a current PD, and many won't want to "waste their time" assessing applicants without that first. No one wants to inherit someone else's problem. Also PD's can be a relatively tight knit group, if I take a PGY-1 from some program into a PGY-2 position, that might leave that other program with an open spot and I don't want to be seen as poaching people from other programs (this is less of an issue in IM where prelim IM interns can fill PGY-2 IM positions).
Is this the match's fault? No, the match has nothing to do with this. Although you got your position in the match (obviously), that's not because of some evilness in the match, but simply because programs that were higher on your list desired other candidates. I don't know what that happened, but it would have happened with or without the match. Perhaps some additional introspection into that would be helpful. The difficulty residents face switching from one program to another mid-training has nothing to do with the match at all.
You're disappointed, and that's a completely reasonable emotion to have given the circumstances. Trying to switch programs is going to be an uphill climb. Your matched program may be much better than you expect. Focusing your energy on switching programs and on maximizing your success in your future program may be at odds with each other, hence may backfire if you focus on switching and are unsuccessful. You mention "3-7 years" which suggests you're considering a fellowship of some sort -- switching programs can make that process more difficult also (if you're in a 3 year program and apply for a fellowship at the beginning of year 3, if you switch that ends up being the end of the 1st year of your second program, and you may not have enough connections / research / etc to do so generating a gap year).
Best of luck, whatever the future brings.