Ron Edwards is no Isaac Newton. He isn't even Robin Laws.
Of course not - obviously so for Newton!
Burning Wheel?
1. People who do play it seem to be confused by the system and are always dropping parts of it or ignoring them or having to consult Luke to clarify them.
2. The system, when not hand-sold or supported by the author, isn't very popular on its own. It isn't an ambassador for itself. This isn't bad by itself but it does suggest something's rotten in Denmark.
3. The people who do like it don't tend to be real exciting or interesting people.
4. Huge parts of it are explicitly (explicitly: the author said so) designed to prevent abusive GMing and play practices which should actually be dealt with interpersonally rather than trying to systematize them away. The game has a huge overhead of rules that merely exist because Luke's game group was/is disfunctional and he made rules to route around that rather than dealing with it.
5. Played RAW it plays like the best comedy game ever written.
Now you could say that 1 applies to D&D but definitely not 2 or 3. And all 5 together? That's a thing.
I could be nuts here but everything I've observed suggests BW is exactly as popular as the players are close to Luke Crane and his (massive and dedicated and long-running) personal advocacy for it.
I don't know how I heard of BW - maybe from
Dan Davenport's review on rpg.net, but maybe I read that after I bought it? I remember that I bought it (revised ed) from my local RPG shop because I'd heard of it, it sounded interesting, and it was relatively cheap. (Maybe $40 - Australian dollars - for two books.)
Anyway, the tagline for that review is "If you've ever wanted to combine the powerful emotions and epic grandeur of Lord of the Rings with the brutally detailed combat of RuneQuest, then boy, do I have the game for you!" That's a reasonable fit for me and my group.
On your points:
(1) The systems are meant to be optional/flexible. I think in this respect your comparison to D&D is apt.
(2) The popularity of the system with others isn't a big deal for me - I ran Rolemaster for 20 years, after all, and that is now a system that I think has very little following.
(3) You might well find me an unexciting or uninteresting person. I suspect so would Vincent Baker and Paul Czege, for that matter. I don't know that anyone finds me very exciting. The main people who tend to find me interesting are fellow academics, or non-academics who are interested in political/social/philosophical ideas.
(4) I haven't experienced this yet, unless you mean the rules for Beliefs and Instincts, or maybe the Trait Vote - in which case I haven't found it a "huge overhead". The biggest overhead in the system, as I experience it, is in the advancement rules, which are a bit like RQ's but with more bookkeeping. To date, the payoff in comparison to RQ is that the advancement rules mean that players don't always have an incentive to make their dice pool as big as it could be - which deals with a whole lot of issues that arise when there is no incentive for the players not to maximise their dice.
(5) I haven't encountered this yet either. I find in play that it is very gritty, especially in comparison to 4e. Maybe there's something that I'm missing?
(6) I've never met Luke Crane or interacted with him (unless he posts anonymously).
But if you point out Rolemaster isn't necessarily "sim" in any way you have to turn the car around.
Have you played very much Rolemaster?
RM can be played in a manner that Edwards would call "vanilla narrativism". I know, because I've done it. For 20 years. It's also incredibly heavy sim. (What Edwards would call "purist for system".) These sim elements can cause issues when running the game in what Edwards would call "vanilla narrativist" style. I know that too, because I've experienced it. Reading Edwards actually helped me sort it out.
The fact that Edwards thinks a game can't be both S + N is not important to me (maybe he would label the sort of game I played "vanilla narrativist with a heavy exploratory chassis" - I don't know, and it's also not really that important to me). What was helpful to me was that the tensions he identified between some of the tendencies of the system and some of the things my group was doing with it are real, and his discussion of those tensions helped me manage and resolve some of them in play.
ALL the predictions made by a theory have to be correct, not some cherry-picked ones.
On that measure every social theory ever produced is worthless. I think it's the wrong standard. It's even the wrong standard for mathematical physics - a system might produce false predictions, because there is some phenomenon present that the system doesn't account for, yet otherwise be broadly sound.
For instance, classic electromagnetism predicts that atoms can't exist with a nucleus of positively charged particles, because the particles would repel one another. In fact, it turns out that that prediction is wrong, because there is another force at work - the strong nuclear force - that was not know to the theorists of classical electromagnetism. That doesn't make their theory worthless. It doesn't even make it wrong.
In the field of sociology, Durkheim makes predictions about the relationship between law and widely distributed attitudes that are, in general, false. At a minimum, he doesn't account for colonial/post-colonial contexts in which laws are parachuted in by an external authority. His theory of technocratic law-making is also poorly developed. Still, I think most people who live in industrial economies who want to understand some of the basic dynamics (political, economic, social) of the societies they live in could do a lot worse than read Durkheim.