Taking as step beyond metaplot - there is an actual story, a notable main character, and a set beginning middle, and end. Player's exist withing this story, may even meet or see the main character in a "" manner, but mostly the characters are involved in their own little side stories for however long the main tale takes.
For example, this morning I had an idea about an Anime space opera like setting. There is no FTL travel per say, but there are different levels of space, the greater distance you travel, even if you are at the same speed. (Rough analogy to minecraft's Nether where you cover 8x the distance of the overworld.) However, the deeper you go, the faster you age, and often violent psychological effects affect most adults. These effects are somewhat countered by either very rare immune individuals or using children who are far less affected. Traveling in the lower spaces is a bit like being in a cloud bank or underwater, reducing the effectiveness of sensors, so space fighters and patrols are a justified part of this.
If this were an actual TV show, it would be following one particular little girl who has somehow acquired a McGuffin that may allow access to zero space or above (ie heaven, or places where time flows backwards) and the possibility that this could allow telephoning supplies or longer periods in lower space areas and thus a better chance in the interstellar war that is going on (isn't there always an interstellar war?)
Since its not, this instead focuses on the set three month period this is happening, elsewhere on her ship, and its just the set 90 day period of life for certain characters. A lot might be going on, but they're not determining the course of events, and the game terminates at the end of the show - possibly even if plots are not resolved. (As an aside, perhaps they can spend XP not just on themselves, but "viewership" - ie pay in to get another season of the series and continue. Otherwise things can just lapse, and the game starts over.)
So would it frustrate you to realize that your adventures are just a sideshow that could be terminated once someone else achieves something? Or would the idea of a game that is same plot, but played multiple times from different side characters wear out its welcome too quickly?