Why do it in the first place?
One answer among several: because "a character that values
intelligent life, whether human, demon, or other," is not exactly an extreme implausibility in Exalted. And if Malfeas's sneezes are worse than the worst of Creation's apocalypses, that character is going to ultimately find Creation a trivial footnote compared to what's happening in Malfeas, of necessity.
And that's bad, because Creation is where the game is.
Like, in actual real life, we as finite human beings say, "Okay, I can't stop World War X, but I can take a cup of soup to my sick neighbor." Our humanitarian deeds don't get swallowed up in the immensity of tragedies we're unable to prevent, because they're too big for us. But Exalts don't get to just say, "Oh, nothing I can realistically do there" - the
heck you can't. Maybe you can't
fix Malfeas, but if you could make
orders of magnitude more difference by creating
any improvement at all...
I mean, maybe you're not obliged to be optimal, but that's a pretty awful distraction. "Yeah, I saved the entire east. But with that same amount of effort, if I had protected a single layer of Malfeas, I would have saved ten thousand times as many sapient beings with hopes and fears and dreams of their own. Go me."
That's not going to bother everyone, but for people that it does bother, it's, uh, going to be a pretty big problem with enjoying the default setting. To which the follow-up seems to be: so if we can remove this awful distraction for a category of player/character types, what do we lose by having Malfeas
only be, say, as well populated as Creation itself -
merely a half-billion or so inhabitants? What narrative space does that close off?