And my friends would include "What does World of Darkness really mean' and all of the other RPGs that we played. It's not liited to D&D. D&D is the first and biggest, but the conversation about RPGs isnt limited to it.
Of course conversations about RPGs aren't limited to D&D. I feel like I'm taking crazy pills?
Look at some of the threads- or just your own comments. To you, D&D is successful because it's a brand. Or (as you wrote before) because it's "fun." Cool! That is totally fine.
You want to have conversations about World of Darkness? Awesome! Have them! Or, for that matter, Torchbearer. Blades in the Dark. Fiasco. Neon City Overdrive. 2400. Twilight 2000. Heck, you could have conversations about any game you want to.
Here's the thing, though. If you try to have a conversation about why
D&D (and 5e) "works" or "is successful" or even "why people like it," you get immediate pushback. For some reason, the idea that D&D is a
designed system that embodies deliberate decisions is somehow considered ... uncouth? Not avant garde enough? To have a discussion about why a game might be appealing to lots of people is ... well, we can't talk about it, because it's just a "brand." And because we can't talk about it, we end up passing over in silence a great deal of what makes it interesting.
A long time ago, I had a good work-friend who had an old industrial '30s poster about some menial factory task that broke down a really simple job into 40 discrete steps (think sharpening a pencil). I always thought it was some kind of arch-ironic joke about the drudgery of modern life. Anyway, I asked him about it one day, and he told me that it wasn't. He was a UI guy, and he kept the poster to remind him that even the simplest thing, even the things that are most self-explanatory, have to be broken down into the component tasks if you want people to understand it. Sort of a version of your elderly relative asking you, "I don't see an escape key," and you have to say, "E-S-C." Or, if you're highfalutin', "S/Z" (you know, Snarf Zagyg).
All of which is to say that there is a lot of fascinating issues that go into the design of D&D- it has freedoms and constraints that other TTRPGs do not have. For that matter, other games have the (relative) luxury of being able to design in the "not D&D" space (as
@TwoSix aptly stated).
Unfortunately, when a person tries to have this conversation, one of two things (or, often, both things) happen:
1. It's the brand! The conversation gets derailed by those who wish to only talk about what brands mean.
2. The other thing. I do not wish to summon it, but let's say people who wish to discuss other systems, and the matters of them.
Both of those conversations are fine things. But look at this thread- it's D&D specific, it's discussing heteroglossia within that context, and it's an attempt (whether good or bad) to analyze D&D on its own terms. And yet, it doesn't stay that way. Instead, it's replete with the same conversations that D&D is only successful because it's a brand- which completely short-circuits any attempts to understand why D&D employs its design, and what it means to have a "D&D system" as we do.