Hussar
Legend
It currently doesn't.
And there is no guarantee WOTC will update it.
That is 90% off the problem.
Greyhawk is freaking OLD.
To match 5th edition's mechanics, assumptions, and content, Greyhawk needs an update.
And there is no guarantee WOTC will update it.
A not-updated Greyhawk is a poor education material.
You would be forcing new DMs to do something with the knowledge to do it.
And here is the Catch-22
An updated Greyhawk has no charm. It's just Alt FR.
I disagree.
But to clarify, what do you believe needs to be updated in the setting? Races are the obvious one, but that’s not really much of a change. Tieflings come from Iuz. Dragonborn have always been around. Heck there’s lots of terra incognita in GH. Plonking a Dragonborn nation in the Hellfurnaces is easy.
What else?