It's not arrogance to introduce non-official rules material to a game; I don't know your experience, but for people like Russ and myself, we have the perspective of having met a lot of these professional game designers in person, and seeing how the only thing that separates us from the "professionals" is experience and collaboration, both of which are not hard to attain these days if a person wants to.
Mearls, Crawford, even old-timers like Gygax, Lisa Stevens, and Monte Cook were cobblers, marine biology students and amateur writers before they were game designers. They're standing on a FREAKIN' GIGANTIC MOUNTAIN OF FAILURE that we don't see because we just see the honed finished product. That's kind of comforting - to be a game designer, you don't need tons of innate talent and years of specialized training - you just need to start somewhere. Same with DMing, for that matter, as most of the people in this thread know quite well.
Old quote attributed to Gary Gygax, writer of AD&D, one of the "founding fathers" of the hobby: "The secret we should never let the gamemasters know is that they don't need any rules." I vaguely remember Mike Mearls paraphrasing this very thing on these forums about three or four years ago, though I can't find it now.
http://www.allenvarney.com/rev_04a.html