I'm not sure we're talking about the same things, because I don't disagree with anything you just wrote.
What bothers me is the idea, which I encountered several times during this network of debates, that being in fandom informs all of one's creative work. The idea that "fanwork" isn't complete unless it includes "original" is something I don't personally understand (because I think of them purely by the distinction of "is this set up as a derivation of a nameable work by a nameable author" and thus exclude history-based etc. creations from the "fanwork" pool, never mind original stuff) but it's not something that bothers me much.