This is going rather far afield, and might be better for another thread, but I've always found Greyhawk to be staggeringly hard to get into, because of a dearth of good materials
I'd never heard it described as an actual campaign setting release, I'd always thought that was just an update for metaplot events. That was one reason I'd never tried to track it down when I became curious about the setting.
I know that in 1998, when I was first getting into AD&D and was learning about it, when I was curious about Greyhawk (largely as the place where all the named spells in the PHB came from), when I asked about it, they pointed me to the used book shelf and said that they often get used copies of the 1e Greyhawk hardcover in and that was the last general introductory work to the setting that had been made.
I know that in much of the AD&D 2e era, it seemed TSR was actively trying to kill the setting. The 1996 Planescape book On Hallowed Ground literally said that Oerth was dying and its gods fading from existence and that people beyond that world knew it wouldn't be around much longer, and that at most a handful of the Gods of Oerth might survive if they got followers on other worlds. I always took that as an implied editorial note from TSR at the time that they didn't want to do anything with the setting.
There really hasn't been a good way for players to get into that setting in a very, very long time. Certainly nothing as accessible or approachable as the various Forgotten Realms books, or even the 3e Dragonlance campaign book.
For what was one of the original, core settings of D&D, and what was the presumed default setting of 3e, they did absolutely nothing with it for a very long time other than Living Greyhawk, which, if you weren't RPGA, was something people generally ignored.
Hence my suggestion that if WotC was looking at things they could have done with 3.5e instead of tossing it out to make 4e, they could have produced Greyhawk setting materials, (or other settings, which had been treated with equal disregard during 3e).
Yes, WotC had pressure from corporate to do otherwise, which was a critical flaw. That same corporate mindset is what gave us the toxic, alienating 4e marketing "3e is WrongBadFun" campaign, after all.