99% of the galaxy is unexplored, that leaves a lot of potential to tell new stories.
The whole concept of running away while the galaxy is fighting for its existence is defeatist in nature, so it does in a way render the whole point of saving it moot.
I've brought this up several times - but the whole 99% thing is inaccurate. It doesn't matter much, because the galaxy is unfathomably huge, but we know with certainty that the relay network does NOT cover the entire galaxy. Indeed, we even know that primary relays (not secondary relays) are separated by an average of thousands of light years, leaving vast swaths of space uncovered by the network and unfeasible to access via conventional FTL.
Why this is, is never explained. We know that there is a large region surrounding the center of the galaxy by about 15,000 light years in which life bearing planets are rare or nonexistent. Personally, I suspect that the Reapers merely seeded relays in the galaxy in all star systems that could potentially give rise to life over billions of years (as well as systems containing valuable resources), of which the number would be significantly lower than the total number of stars in a galaxy. Creating a network otherwise would be enormously wasteful and impractical.
Thus, it is consistent with canon that the network covers only a small fraction of the stars in the Milky Way, via direct relay travel between primary and secondary relays, and conventional FTL in a reasonable radius out from all relay systems. This fraction is unknown, but to throw out a number - if the relay network covered ONLY 4% of the Milky Way, that would still be approximately 8 billion stars on a very low conservative estimate, and 16 billion on an upper estimate.
That is absolutely massive. There are PLENTY of stories that could be told in unexplored regions of the Milky Way relay network. So, does the network cover all 200-400 billion stars of the galaxy? No, it definitely does not, and people repeatedly saying it does, doesn't make it true. But even a very, very, very low estimate has it covering billions, as the galaxy itself is huge.