Granted, the treatment of the Forgotten Realms as a brand, by both TSR and WotC, has often been less than ideal, to put it very charitably. Indeed, Jeff Grubb's introduction to the DM's Sourcebook to the Realms (one of two books contained in the boxed set) makes this quite plain:
About midsummer of 1986, TSR was shopping for a new world. We had experience in world-building under our belt, with two versions of the WORLD OF GREYHAWK campaign setting, and the creation of Krynn, home of the DRAGONLANCE Saga. This time, we were after something different; a world that we could continue to develop over the years that will follow, and set all future AD&D game modules into. A place where a variety of talented individuals could all contribute to its creation and its development. Rather than one view, a combination of views that would grow and develop through adventures, sourcebooks, short stories, and books.Please take note of the of the bolded section in the quote. As it turned out, TSR did not in fact set all future AD&D modules in the Realms, but they certainly made a good effort at it, producing reams of Realms-related products over a very short period of time. In the process, they certainly gave the impression that AD&D and the Forgotten Realms were synonymous, an impression that left a bad taste in the mouths of D&D fans.
Coming as this did so soon after the ouster of Gary Gygax from TSR, a mythology has grown up around the Realms that I think is both untrue and unfair. If one examines the Campaign Set on its own merits, it's not much different than what was found in the 1983 World of Greyhawk boxed set. There's more room given to NPC descriptions, it's true, but the vast majority of those NPCs are 9th level and below -- precisely the sorts of people with whom an average adventuring party would likely interact. There are a handful of higher level NPCs, including the much-reviled Elminster, but their descriptions make them appear almost as "scenery," no different than describing noteworthy cities or landmarks. There's little implication that Elminster or Khelben Arunsun are traveling the world, righting all its wrongs. If anything, the implication is exactly the opposite: evil in the Realms is too strong for any one person or group of persons to overcome, which is where the PCs come into play.
I think it's here that one of the largest fault lines lies for those who dislike the Realms. The Realms in unambiguously a world in need of "heroes," not merely "adventurers." A Realms character is far less likely to be venal and self-interested, doing good more by accident than by design. As a fan of morally ambiguous protagonists, I can certainly appreciate this critique of the Realms, even if I don't find it a damning one. Not all fantasy literature is Howardian/Leiberian swords-and-sorcery and not all swords-and-sorcery tales exist in a moral vacuum. There is room for a type of fantasy where fighting evil is the primary focus.
The problem, I think, is that, when the Realms made their debut, TSR attempted to push the setting as its sole vision of what D&D was and should be. You either signed on to it or you were left out in the cold. At least that's how it appeared to many gamers, who soon resented the Realms and its popularity, all the while forgetting that much of what they disliked about the setting had more to do with TSR's marketing than with any essential qualities of the setting itself. If one looks carefully at the original boxed set, what you find is a wild world beset by evil, where communication and travel are slow and local problems loom far larger than epic, world-shattering plots.
Ed Greenwood's own campaign was far more localized than was Gary Gygax's Greyhawk campaign, for what it's worth, and the power level of the PCs much lesser to boot. And this is all quite clear in the original boxed set, whose treatment of most topics is sketchy and suggestive rather than definitive. It's a superb sandbox setting for heroic fantasy. Now, not everyone wants a heroic fantasy sandbox and there's nothing wrong with that. However, I think it unfair to expect the Realms to be Greyhawk or Nehwon or the Dying Earth; it was never intended to be. What it is is the product of a longstanding D&D campaign, played by real people, which puts it head and shoulders above many later beloved TSR settings who owe their origins solely to finding new ways to squeeze yet more money from the game's fanbase.
If I sound defensive on this point, I apologize. I make no bones about the fact that I have been a fan of the Realms since I first read Greenwood's articles in Dragon. His setting always struck me as the kind of campaign I wish I had run -- not just the setting itself, although I did love it, but also the group of regular, steady players whose characters grew slowly over time and many exciting adventures. That doesn't blind me to the fact that, over the years, the Forgotten Realms product line has included many, many silly things and has thrived on a constant stream of auctorial one-upmanship in an effort to sell more supplements and novels. But I don't think that has any more bearing on the quality of the original Campaign Set than does the existence of the Rose Estes Greyhawk novels (or, for that matter, the later Gygax-penned "Gord the Rogue" books) have on the World of Greyhawk.
Critics often forget that the Forgotten Realms Campaign Set was the last campaign setting released for First Edition. Though the 2e era is where the Realms were flogged to death, it was 1e that gave birth to it and that's quite visible in the product itself, if one cares to read it with unbiased eyes. In reviewing my copy for this retrospective, I found myself able to forget all that came after it and enjoy it for what it is: a huge, wide-open setting drawn in broad strokes, just waiting for individual referees and players to fill in the details -- exactly what a good campaign setting should be.