Player characters tend to need more framing and bonds to the setting than random monsters. They are going to be in every session and who that are in the setting matters a lot more than a random 4 armed blue gorilla that is killed in a fight.
In shocked that so many people are saying "Nah. It'll be fine" when not having a place in a setting is a Top 5 reasons DMs ban races and classes.
Okay, let me fix it for you.
Here was the original text for Orcs from the wiki:
Orcs believe that in order to survive they must expand their territory, and so they are constantly involved in wars against many enemies: humans, elves, dwarves, goblins, and other orc tribes
Now, I shall magically create a place in the setting for good orcs. Ready? "
Some Orcs believe that in order to survive they must expand their territory, and so they are constantly involved in wars against many enemies: humans, elves, dwarves, goblins, and other orc tribes. Others have made treaties with their neighbors, and lay claim to the wild lands those neighbors cannot conquer"
Tadah! Now, here's the real question... did I even need to do that? Could I, in the course of making examples of the land, have just... named two orc tribes, one set on conquest the other with a trade deal?
What about the goliaths? Well... they are related to Giants, they are giant-kin. The giants exist in Oerth. The Firbolgs are already there, and you just need to... have the same lore for Goliaths that they currently have. Mainly
: Towering over most folk, Goliaths are distant descendants of giants. Each Goliath bears the blessings of the first giants—blessings that
manifest in various supernatural boons, including the ability to quickly grow and temporarily approach the height of the Goliaths’ gigantic kin. That completely works, no need to make them Half-Giants, they aren't half-giants. Where do they live, well, this is what it says about Giants:
Giants are found throughout the Flanaess, though the vast majority of giant populations are concentrated in and near the Yatil-Hellfurnaces and Corusk-Rakers mountain chains. So... same thing works, right?
Why did no one see them before? Well, both of those mountain ranges are in the distant, far-off lands. Or maybe they migrated here from across the desert or the ocean.
The issue isn't "DMs are going to ban these things at their table because WoTC didn't properly place them in the DMG example chapter on how to build a campaign setting and ruined the sanctity of Greyhawk!" The real issue is people who are going to demand THEIR version of greyhawk remains unchanged from the 80's because anything made by WoTC is stupid and dumb and ruins their perfect setting.