What this game should do to increase longevity

[AnimaAnimus]

And that would be jarring because you're potentially leaving plot points unresolved or you'll mess with the timeline of the story too much.

Not if each story was its own thing. Going back to my previous example. If you wrote a book about a political coop or existential threat set in India that was happened in the same time line as the US Civil War, how could there possibly be any unresolved plot points? Even if the main protagonist was American, there would be no cross over because the story you are reading occurs completely in India.

Many games handle story telling like this and it actually works incredibly well.

What I'm hearing is basically. Stop the main story and just make a different story. That in no way adds longevity.

Conclude. No one is asking them to just stop it bluntly. Just bring it to a conclusion so we can have something a bit more refreshing than "ascians did it" "garlemald did it" or "allagans did it". Every story needs to have a conclusion, otherwise you get the author adding ridiculous things to keep the story flowing. This is why many TV shows are stopping after 3 or 4 seasons even if they are highly popular. Because they have a natural stopping point and if they just keep adding and adding it becomes convoluted and actually destroys the story they wanted to tell.