Okay, maybe not "canon." Let's call it established lore with competing perspectives. We can "Elder Scrolls" this stuff. Many ways to explain the same history, based on competing historiographies. Instead of saying "previous book said X so X is canon," we can imagine each previous book as a particular historian's take on events. Maybe they got information wrong. Maybe they're biased. Maybe it was revealed to them in a dream. Maybe there was a break in reality. Maybe the only real evidence is vague.
Instead of saying that something in the lore says otherwise, so the game is broken, we can instead look to the features of the lore which corroborate the story to situate it within the setting's history and dynamics.
While some may use canon to say that things are broken, I think we should use it to have fun.
