This isn’t quite the case with World of Warcraft for a simple reason: it’s a video game first, a story second.
So, when we get a retcon such as, “The guy who designed the Silverpine Quests somehow completely forgot the Kirin Tor were neutral, so uh… that whole bit with the Forsaken wiping out the Kirin Tor at Ambermill never happened,” the problem arises that the game world never changes because they don’t bother to either update or remove the quests (old content, no incentive to fix it’s narrative), and thus we have an existing retcon that remains like a festering wound.
Later, we get retcons that change the fundamental nature of the setting as we were meant to understand it.
When the Chronicles came out, it was a lore book, word of god, hard canon. Later, when new writers came in and wanted to tell their stories, they retconned the Chronicles to being, “Written from the perspective of the Titans, whom aren’t omnipotent, so if we do anything in the future that doesn’t make sense, its because the Titans don’t know everything.”
That resulted in the Shadowlands, lauded as the worst expansion, period.
When WoW introduces retcons, it’s rarely to the benefit of the setting. Their only purpose for WoW is to allow the, ‘Rule of Cool,’ stories to be told. This riddles the setting with so many holes that it becomes increasingly difficult to understand and, as a result, more arduous to immerse oneself.
A retcon such as Sargeras corrupting the Eredar instead of the other way around did add something to the setting. It made the Eredar far less intimidating an enemy, but we ended up with the Draenei as a result. I’d say this was an example of a retcon that was effective. Most WoW retcons, however, have been to the detriment of the setting.
