Hussar
Legend
Just to add to this.
Any later element, particularly 2024 D&D elements you add to Greyhawk typically don't have enough depth in the setting because you've got forty or fifty years of the setting already. It's a very thin veneer to add, say, Warlocks to Greyhawk since none of the NPC's in the history of Greyhawk are warlocks. Going forward, you could add more about warlocks (or whatever element you care about) to the setting and perhaps, after some time, it would stick. But, it's a very uphill battle.
And, even when it's done more extensively, like in Ghosts of Saltmarsh adding in a Tiefling representative of Iuz in the trader's house, now you have the rather strong push back from fans that insist that you must never change lore. Iuz never had tieflings, so, it must never have tieflings, goes the argument.
In a setting based on what D&D looks like right now, based on the PHB, and Monster Manual of 2024, things would look considerably different from these older settings. The lore surrounding so many monsters has been completely rewritten. Dragons, as a good example, have completely changed from the early days. Early days, dragons were basically Smaug - sitting around on big piles of treasure and not really doing anything. Now? Dragons are political creatures, shaping species, keeping slaves, altering the environment, getting involved for good or for ill.
And this is true for just about every single species in the Monster Manual. Greyhawk predates anything about the Blood War, for example. Drow were just another monster with about five pages of actual lore in the setting. On and on. And trying to square that circle of respecting canon while incorporating change is a Herculean task that very often fails.
