When a character isn't a chosen one, however, they're only involved in what they can plausibly get involved in given their current alliances/abilities/location/whatever, which kinds keeps the plot a lot smaller and more focused on what's happening at that moment.
I think the Witcher books are a good example of the fact that that's not necessarily the case.
Geralt is not a chosen one, yet the plot revolving around him is massive, involving a number of kingdoms and organizations. That's because his profession makes it so that his services can be requested by both the paesantry and the highest places in society, making him a character that can easily move between the various ranks of society, and gets sucked in major plots and big scale events. And yet, he's no chosen one, he's a reject, that everybody scorns but everybody needs.
I personally think that chosen one stories are the lamest kind. Not that they can't be good, granted, but I tend to give more props to a writer who is able to create a character that is involved in big events, is complex and has charisma without the need to make it a chosen one. Such a character is far more interesting and compelling to me than one that's destined to be great or to do great things to begin with.