A player of mine said something very interesting the other day. He said one of the reasons he likes playing in Arunia is because he can really change things—when the PCs alter regions in important ways, they find their place on the OP wiki of the setting and their actions described in detail. This made him feel important in contrast to, for example, every other setting ever designed by TSR. Now, there is something of a false equivalency being made here between a published setting and a homebrew setting; there's nothing stopping me from customizing my own version of Greyhawk, for example, so that it includes the actions of parties the characters have been in. I suppose, yes, the actual manual doesn't do much to support that and it would never reach TSR to be reprinted that HIS character did something special...
But that's neither here nor there. I suppose its important to note that I've always been a fan of the idea that OTHER DMs running Arunia, of which there are precious few, would send me the tales of their parties and I could attempt to integrate them, picking and choosing which made the most sense for the core setting.
Yet, I don't think what my player described is something impossible to achieve in home campaigns running settings that are "all already written." If that is actually the case, then most of my work fleshing out Arunia for other audiences is really for naught. I don't want people to play in a static wasteland of high-level named NPCs who accomplish everything important and deny the players all agency.* So, I can't help but think that writing everything down, codifying it, and sending it out into the world doesn't necessarily kill campaign setting, making it into some stuffed taxidermy of itself.
Vitality is one of the most important elements that I strive to emulate in my work. The vitality of change is sometimes very difficult to achieve in both fiction and D&D. Things are always happening all around us, outside our own scope of knowledge. This is one of the reasons I love the Hill Cantons rumors postings and have started doing a few of my own every so often: these rumors are the things which help make the setting feel vital. There are forces at work larger than the players, offstage in parts of the setting they aren't seeing, or with plans they haven't even begun to fathom.
Living history is another element of this vitality. Making a mark on the setting is extremely important. One of the great joys of play is retiring an adventurer to have them become an NPC that can be met later. Relinquishing control of your character is only a victory condition because they become integral to the setting, and may receive their own entry in your DMs homebrewed encyclopedia or setting guide. You yourself get a chance to become permanently part of the world, the PC-fragment of your personality embedded forever in history.
*I also don't want the players to be the ONLY ones capable of exerting agency in the setting. I like a world that can get on without them, as much as that contradicts part of the Great OSR Player Agency shtick.