They're aliens. All of them. If they don't originate from this planet, then they are alien to it. Doesn't matter if they're from another dimension, another planet, or another universe. Doesn't matter if they're corporeal or physical. Angel, demon, or extraterrestrial. Good, evil, or indifferent. Originating from somewhere else other than Earth means it's alien to Earth.
This is what needs to change about the other aybwe see this issue.
And it doesn't necessarily mean it's a bad thing, either.
They're aliens. All of them. If they don't originate from this planet, then they are alien to it. Doesn't matter if they're from another dimension, another planet, or another universe. Doesn't matter if they're corporeal or physical. Angel, demon, or extraterrestrial. Good, evil, or indifferent. Originating from somewhere else other than Earth means it's alien to Earth.
This is what needs to change about the other aybwe see this issue.
And it doesn't necessarily mean it's a bad thing, either.
There's one more option: they could have been on Earth all along, but living either underground or under the oceans.