There's a really good interview here (WARNING PDF LINK!!!!) with Rick Priestley and John Stallard that was published in Battlegames in 2009. It's from when Rick was still working at GW. A lot of it is just three old wargamers reminiscing about the 1970s but there are some interesting bits in there about GW's approach to wargaming.
There's a fascinating passage here that I think, coming from the mouth of a pro games designer, is very illuminating about the rise of the OSR even though it's actually about wargaming and GW's approach to this:
I was quite relieved to read this to be honest as I always thought my information retention skills had atrophied since puberty but apparently that's the same for everybody. It's why I hate long, complex rulebooks now in my 30s even though I was a sponge for such in my early teens. It would also explain the amazing popularity of some games that require the player to juggle many pieces of knowledge in his skull at any one time, such as exceptions to the main rules and "special abilities" and the like.
I think Rick hits the nail on the head here even though he isn't talking about D&D.
OK what he is actually talking about in the interview is a masterpiece of diplomacy. The subject of Warhammer being quite unsophisticated is obliquely not-quite mentioned, and Rick therefore doesn't quite justify, explain and apologise for it. What Rick sorts of hints at is that Warhammer was quite deliberately written in the style of wargaming Godfather Don Featherstone and aimed at the same sort of teenage boys who got into wargaming via his works (such as Priestley and Stallard) and was a deliberate move against the complex and allegedly sophisticated rules of the late 70s/early 80s but everybody is being just too nice to mention all that.