Now, here's a question. You say that you are using this setting with multiple groups. Presumably those groups are not connected - they aren't the same people.We'll just never agree on that. I've run a persistent campaign for decades with multiple groups. I value consistency and campaign theme more than running a campaign by committee.
I wouldn't want it as a player either.
Do the players actually care? Do they actually care what happened in another campaign that they had no connection to? Do they care that you decided fifteen years ago that X was true in your setting? I get that you care. Fair enough. But, do you really think the players do? IME, they most certainly don't. There is no consistency because they didn't experience it.
The only link they have between themselves and the setting is you. So, they sort of have to care about setting consistency because you insist on it. They don't really have a choice. Because you've decided that a setting decision made years ago that is in no way connected to the current players must be consistent, they have to roll with that. And, because you will not allow the players to add to the setting, you've pretty much self selected players that won't add to your setting.