And don't tell me, "oh, the core setting is the D&D multiverse with Eberron, Forgotten Realms, Greyhawk, and everything else altogether", because to me that's just WotC wanting to have its cake and eat it too.
Either have a core setting, and design the system around it, or don't and create a truly neutral rules system. Don't try to have it both ways.
In It's defense, D&D has done a fairly good job at taking advantage of its market leader status, and having its cake and eating it too.
D&D has always been
very coy with its implied settings... It has
always tried to have it both ways.
Luckily being the market leader; most players squint or ignore what they want so that they can say that they are playing in their 'unique' setting.
But in reality the 'unique' D&D setting = "Parts of D&D I restricted or house-ruled to do what I want, keeping the rest of the base D&D setting and genre assumptions, and calling it 'unique'."
hose above 4 lines don't really define a setting, they define a genre of fantasy. It's not setting specific as it can be applied to innumerable works of fantasy fiction. It can be applied to Tekumel even! This is not setting specific in any measurable way.
Except for the fact that mechanically in the PHB and DMG Lots of setting specific assumptions are made. Particularly in Cosmology and Magic.
How Cosmology and Magic in the PHB and DMG works and effects the core classes is a HUGE setting assumption baked right into the D&D rules.
D&D is not 'generic fantasy' by any measure. It has been and always will be its own style of 'D&D fantasy'.
...What they want is a "generic" fantasy system that will work for their own personal setting out of the box-- which is impossible-- and one that says D&D on the box and is played by millions of other people whose own personal settings are not theirs.
So much this.
If you are playing D&D out of the three core books, you are playing
D&D Fantasy. You may dress it up with various setting veneers to give you a 'different feel'. But you are still very much playing
D&D Fantasy. Too many genre and setting assumptions are hard wired into the core system.
Pathfinders Galorion is a simple tacit acknowledgement of this fact, which is then leveraged to sell their AP's.
But as in my reply to King barber, TSR and now WOTC D&D has done a fairly good job of selling 'D&D Fantasy' = 'Generic Fantasy'.
The fact is that the game tropes of D&D have been so influential on the fantasy genre that D&D forms many people perceptions of what fantasy is. So to many people 'D&D Fantasy' does = 'Generic Fantasy'!
It makes for a nice self reinforcing feedback loop that has allowed D&D to have it both ways for decades now.