This thread really opened my eyes. I was so confused by the conflicting opinions of the very terms the OP was discussing that I went and read the GNS articles. That simplified everything.

Holy cow! I'm a lawyer and used to dealing with terms that are defined specifically for the brief, but that is overkill. I am now confident that no two posters in this thread are talking about the same thing.
If you buy the GNS, then "simulationist gaming" is an oxymoron. If you are "in it to win it" it is a game and the players are gamist. ANY choice that allows one to mechanically alter a character begins to destroy simulation. "My character spends three months practicing archery, so her bow attack gets better." Sim? Not according to the GNS. It's gamist because the player implies his willingness to "Step on up" and meet a combat "Challenge" via the expenditure of "Currency" (time in game) to improve the character vis-a-vis the rule set.
If this is the definition of gamist, then D&D is 100% gamist and always has been.
If the definition of "sim" is "internally consistent rules that make sense within the genre" then D&D is and always has been 100% pure "sim." The genre is "D&D." By definition, it is internally consistent with itself. The complaint has to be based on some other genre that the complainer is using as a base-line. The ring issue is a perfect example. The "I want a sim" camp complains that it isn't realistic that a ring can't be used until the 11th level. Compared to what universe? I'm wearing a ring right now and, try as I might, I can't get it to do anything magical (except guarantee that my credit cards are maxed). In what genre did the callow youth setting out on his first adventure have mastery over the power of a magic ring? (the one ring being an artifact for purpose of this discussion) How is it internally inconsistent for a 1st level character to put on a ring and be told "though you can sense great power untapped within, your efforts to reach it are thwarted by a powerful resistance?" If that same character were 10th level, would he not then be told, in perfect consistency, "the torrent of power contained in this ring is tantalizingly close. You press against the barrier with your will and feel the barrier stretch thin. . .but hold."
Every complaint I have heard from the "sim" camp boils down to "I just don't like this rule."