Remathilis
Legend
I mean, if one is trying to use Gary as some sort of "I win" button--other than to point out pure historical facts, I guess?--then they've made a self-defeating argument. It is trivially true that D&D is not exclusively what Gygax personally created, because so many versions of it have been written by other people. Gygax is no more the sole arbiter of what is or could be D&D than, say, H.P. Lovecraft is the sole arbiter of what is or could be Cthulhu stories and cosmic horror generally. Yes, the genre owes an enormous debt to him, but even during his lifetime other people were already writing stories about Cthulhu and Nyarlathotep, and he himself "borrowed" Hastur/The King in Yellow too.
He basically gets trotted out like one of those Original Intent/Strict Constructionist arguments. The way it was is the way it should be attempts to slow or stall change. Hence you see things like "as Gygax intended" or similar when arguing about how the game has moved on from the early playstyle. OS gamers will treat him as a patron saint or prophet in such arguments. He's mythologized as some font of ancient wisdom when he was a talented creator but certainly not the only one nor are his ideas immutable truths.
So yeah, I respect the man, but his way isn't any truer or more pure than any other