"Simulationism", in the sense that the mechanics of a RPG should yield the fiction with little need for anyone to decide/inject their own view, has always been a minority approach to RPGing I think. RQ, RM, GURPS etc exemplify this, but they have never been predominant. 3E D&D seems to be the closest that D&D got to this, but it has so many other mechanical elements (both inherited from earlier D&D as well as of its own invention, like multi-classing and feats and so on) that it isn't really a sim game in this sense.