Uh-oh, here comes a longpost.
I never ignore solid and confirmed lore–even when I personally think it’s bad, boring, a really cringy retcon, or just an absolute slog to RP through (cough cough BFA cough)–because solid and confirmed lore is what makes up the WoW universe in the first place and allows all us roleplayers to play on an even playing field, so to speak. There are plenty of grey/untouched areas of the lore where one might find plenty of wriggling room, but the 100% Written In Stone Stuff? No dismissing that, ever. How do you reconcile a character who ignores certain parts of content with a character that doesn’t? The answer is, you don’t. And since there is no community without reconcilation and no RP without a community, this is something important that we should all work on preserving.
Note: of course it’s perfectly valid if your character ignores the lore due to their own IC ignorance. Say, a troll who never saw Teldrassil and claims that the tree never burned and it’s all just anti-Horde propaganda could be genuinely interesting to interact with. A nelf who decides that the War of Thorns never happened so they can continue RPing in Darnassus and proudly announce that fact to anyone willing to listen, though? Yeah, nope. Whenever I meet a player like this–a player who abandons the Even Playing Field–my own character will just assume that they are just mad from grief/delusional/drunk/completely bananas.
If you choose to do something like this, you are actively alienating yourself when it comes to general RP, or at least the kind of RP that goes deeper than your typical surface-level small talk which usually occurs in walk-ups or open social RP. This is also why I believe that no experienced RPer worth their salt will ever be caught dead RPing as one of the actual Heroes of Azeroth (or, as I like to call them, All Those Damn Highlords With Actual Ashbringers), or anyone related to the big lore figures (or, as I like to call them, All Those Damn Sons of Arthas). Creativity is fun and all, but one must never forget that RP is a group sport.
To answer the second part of the question… While I never ignore the lore, I do pick and choose the capacity in which I OOCly interact with it. Shadowlands in general does nothing for me, so I am very happy to skip the events my guild does there and instead remain on Azeroth, where my characters have plenty of work to do (thanks, Scourge!). My characters acknowledge everything that happens in the lore (to the extent they are reasonably capable of learning of it, of course) and all the guild lore that is generated there, but I personally just choose not to participate in the RP that goes on there on the excuse that my characters were somewhere else, doing something else. Not to mention most of them are small fries who would never even step foot into Oribos.
As for the Blizzard plot turning the PC into The Hero… Well, the line I draw between IC and OOC is red and a mile wide, so it’s not a big problem for me because what I do in raids/PvE is completely disconnected from what I do in RP. Linaria Duskweaver will remain a snotty Magistrix with some really shady hobbies no matter how many raid boss mounts I have sitting in my collections tab.