Werthead
Explorer
As for the canon topic, I've always wondered, when talking about canon in the context of D&D (or any fictional franchise), and people mentions "this is/is not canon": is "canon for what?". Because canon is only useful when you trying to "study" something ("I'm reading this series of novels; is this novel relevant/canon to my reading order, or can I skip it?"), or when you're doing a professional or semi-professional research on something (like, writing an article for a wiki).
When you are worldbuilding, canon become less useful. The only use for canon in this context (for me, at least) is when you want to be as faithful to the source material and, as someone mentioned before, for some settings it may be impossible to be really faithful to canon (good luck trying to be faithful to canon in the Forgotten Realms). And as soon as your players interact with the game world, you've already deviated from canon.
I see canon more as a tool for understanding/researching something than a holy scripture.
Canon, worldbuilding and lore is a hot topic in fandom generally but seems to be very important at the moment because of the general feeling that many adaptations have been made which try to instantly change the source material for what some feel is no apparent reason (whilst others may disagree and feel those reasons are important).
There are positive/neutral connotations from this, that worldbuilding adds depth and richness to the world that aids in the suspension of disbelief, that it can provide convincing backstory for your story that makes it make more sense, and it creates a sense of coherence to the setting that makes expanding it easier as everyone knows what the ground rules are. It is also a fun intellectual pursuit (Tolkien noting that he enjoyed creating lore for the sake of it, sometimes to the detriment of getting the actual stories finished).
There is also the enjoyment that neurodivergent fans get out of science fiction and fantasy, and continuity errors and mistakes and things not making sense can be considerably more annoying/upsetting for them than for other fans who are perhaps more interested in the story at hand and not every detail.
There are also negative connotations from it, that canon mastery and expertise, especially built up over decades, can be used as a blunt tool to gatekeep fandoms and prevent newcomers from coming on board with different, fresher perspectives that can keep a franchise ticking over and evolving.
I would say that canon/lore is palpably different for TTRPGing than for books (where it is seen as hugely important) and TV shows and movies (which it often exists superficially and can be changed or retconned if it allows for a more spectacular setpiece). I believe in every TTRPG campaign, even in established settings, it's much better understood that the GM is in charge, and even if it's an established world it's still the DM's version of that world. It feels like this did need to be pointed out in almost every Forgotten Realms sourcebook at one point, presumably to counter the issue of players who'd read every Drizzt book rocking up to argue pedantry with DMs who perhaps only had a single FR setting book.
In the case of Greyhawk (circling back on topic!) it's going to be an interesting situation if they are simply picking a year and deleting everything that happened after that point, as that's not typically been done in settings before (Dragonlance is at least flirting with it as well, though, and the new Weis/Hickman trilogy seems to be teeing up a lore explanation for it). At least with GH they have at least some cover in that the amount of post-Greyhawk Wars material is, whilst not nonexistent, not vast in amount and they can probably justify taking it in a new direction (although veterans of Living Greyhawk campaigns might feel aggrieved). Despite frequent requests to do so, I can't see WotC simply deleting the Spellplague from Forgotten Realms and everything that's come since (including the movie and Baldur's Gate III, not to mention all of the 5E adventure paths) in the same way.