A persistent online world with an always progressing historical timeline would be a really interesting concept to explore. Complicated though, as for example you don't really want new players to join when the world is on fire (unless that is your setting).
Some MMORPGs handle this alright (although tbh I only really know FFXIV at this point), where every player goes through their own timeline of sorts - you are The Warrior of Light, and as you progress through the story, you're pivotal in some great events like the defeat of the big bad or preventing the world from ending. That kinda thing. But the world is persistent, so it's only you that unlocks new areas and, in some cases, only you see some changes in the world or some NPCs. It's mostly through what NPCs tell you though.
Yeah I kinda dislike that approach to MMO storylines, it's hard to suspend one's disbelief that you're "the chosen one" when there's a conga line of chosen ones behind you waiting for you to get on with it and start some story quest. Bonus points if they're all clipping through you lol.
There are some that take the MOBA type approach of just letting you go in a not-so persistent world with the story of the season going on that happens regardless if people participate in it or not, but if there are any quests they tend to be kinda generic and get old fast.
There are few that can manage a good middle ground, if any. I could never get into EVE Online but I respect their organic-ish approach to this, where the players make the story.
https://www.medievia.com has a concept of kingdoms and clans will battle to gain control over territory for the kingdoms, so there's a bit of a persistence due to the ebb and flow of clan membership and how they can hold back the other clans.
Some MMORPGs handle this alright (although tbh I only really know FFXIV at this point), where every player goes through their own timeline of sorts - you are The Warrior of Light, and as you progress through the story, you're pivotal in some great events like the defeat of the big bad or preventing the world from ending. That kinda thing. But the world is persistent, so it's only you that unlocks new areas and, in some cases, only you see some changes in the world or some NPCs. It's mostly through what NPCs tell you though.