I was pretty clear in what I was talking about in the OP. I meant lore as in the details. I don't think the details are fundamental to TTRPG play. You can enjoy a game with no particularly detailed lore, because the game is what's in front of the players, not necessarily what's under that.Lore definition?
If you mean lore, as in, here is the world, then yes. It is the literal framework of how the game should run. In fact, the rules should be grafted to the lore. Imagine if a show or author didn't care about their world building lore? Imagine Tolkien's world without meticulous care for lore? Or Martin's? (According to lore, dragons are extinct and there was once a bloodline could ride them. - Nah! Let's just pretend in the middle of the story it's not like that.) So, if you mean lore, as in the construct of the world, then it is a silly question. It has to matter. It's why a halfling is small. It's why dwarves have beards. It's why metallic dragons align towards good.
And before any begins a diatribe, yes there are exceptions. Always has been, and always will. But consistency and group thought are needed to make a TTRPG work.
I disagree with @Reynard that you wouldn't notice. Sure, if they altered a town a little, you wouldn't notice. Or if this one unknown god became a player in the deific world. But, if the lore changed, I believe you would notice right away.
This.Depends on the lore, the canon, the setting, and the campaign world. If I enjoy it, I'm upset when it changes; if I don't enjoy it and it's changed to something I enjoy, I'm glad for the change; if I don't enjoy it and it's changed to something else I don't enjoy, I'm slightly upset as it could have been made into something I enjoy. And this only applies to settings I like. Al-Qadim, Dark Sun, Mystara, Ravenloft, and Spelljammer. Beyond those, I don't really care.
By that definition, if I change the lore for my campaign, it's not D&D either -- which is so ridiculous on its face that it hardly bears further comment.The lore makes the game into DnD
You can take the rules and make other games. Pathfinder and Star Wars and Esper Genesis. They ain't DnD
It isn't just that (although, full transparency, I don't actually care about their feelings or opinions that much). It's that I feel trying to build decades-long consistent lore is actively detrimental to the development of new, exciting stories. I don't see a win-win position here that can be staked out by the IP developer.Choosing to changing something you don't care about that someone else is attached is telling that person you don't care about them and their feelings opinions don't matter