As I posted and you quoted, "How any individual poster deals with the fact that they don't know much about RPGs other than D&D is their prerogative." I think it's fairly obvious that, and how, that point generalises.But then again, that still gets back to a question of what other RPGs one has to be familiar with.
I mean, I don't disagree with your general point, but let's look at a working case. Let's say you have someone like me, but who stopped investigating in new games in, say, 1990. I'm not limited to D&D (in fact, at that point I hadn't played D&D for 15 years), but all the games I had contact with at all were trad games; barring some oddity, I wouldn't even have had the chance to hit much that wasn't.
Is that "sufficient" to participate in discussion? Its still going to bias my expectations, since I'd have had no contact with FATE (even Fudge was about two years off from my cutoff), PbtA, Cortex or any of the evolutionary works of the last three decades. But I'm not limited to only D&D; I have had contact with RuneQuest, Hero, GURPS and Traveler to use four commonly known cases, none of which are particularly D&D like except in the broadest sense.
But if you want to tell me - for instance - that a RPG can't work without a GM-pre-authored map and key; or that any GM improvisation/invention that goes beyond a map and key will almost inevitably result in railroading; then I am going to want to know whether you've played much Burning Wheel.
Or if you want to tell me that Apocalypse World can't handle mystery scenarios, I'm going to query what play experience you're basing that on, given that the book makes it obvious how in principle such scenarios could easily be handled.
As I said, it's each poster's prerogative as to what they post, but if they're going to make claims on a thin or inadequate evidence base I don't see why anyone else should be obliged to take those claims seriously.