To be clear I wasn't saying that D&D emerged in a vacuum or was created whole cloth from nothing. My point was more that:
1) All of us who are in the hobby now, especially anyone making games, is here because D&D got big, and we either were exposed to RPGs through D&D itself or by a game that followed D&D.
2) I think it is far from certain that any of the other games being produced in this community would have hit with the same success and traction that D&D had ---a lot of that is marketing, luck, etc. I think there is a strong likelihood such games would have simply remained in their small corners of the hobby similar to bookshelf murder mystery games. Is it possible something very similar to D&D could have emerged in D&D's absence and also took off? Sure I think so. I just think D&D's success was far from a certainly, and that D&D was far from inevitable.
3) There is nothing wrong with recognizing the significance of D&D. I don't play D&D anymore. I play almost exclusively other systems at this point (and when I do play D&D it is usually 2E so I can use the old Ravenloft books). I also make games that aren't d20 or D&D in any way. But I understand that most peoples frame of reference for RPGs is D&D. I just personally find it counterproductive when people try to promote non-D&D games, even my own, by going after D&D in a negative or dismissive way. Most groups today still seem to be playing D&D or D&D derived games (pathfinder is essentially D&D for example). I am eyeballing that of course. I dont' know what the percentage is. But I know when I would go to game stores or conventions to display my own games, most tables were D&D and pathfinder (granted I haven't done that in a while so there may have been a shift in the past few years)