But if the aliens - on other planets, or other planes - aren't showing up to Golarion to help, then their planets are all disaster areas of their own. And if the desolation is that uniform, it's probably maintained by divine intervention in the places prophecy still holds, every plane except this plane, or every planet except Golarion - the scope of prophecy shattering isn't clear. Or the aliens, if they're more advanced, aren't a kind of thing that cares about the mortals on Golarion. Or the gods are preventing them from helping...
Anybody seeing a flaw in that reasoning?