Can you construct a falsifiable hypothesis involving trans-dimensional beings, or ETs, or something else, and Earth's natural history? Or any hypothesis of any kind? What experiments would we run? What observations can we make? I'm not sure that this counterproposal is actually scientific. Just because it doesn't require a deity doesn't mean it's "science."
You're getting way ahead of yourself, what you have to do first is find the aliens, and then when we meet them you'll be able to make some hypotheses. People believed atoms existed for thousands of years. But atoms weren't actually science until people in the 19th century devised experiments to observe them; until then there was "Atomism," a branch of philosophy, and atoms were mystical, pseudoscientific entities.
If Lavoisier, or Leibniz, had proposed a bomb that could destroy entire cities with the power of millions of tons of gunpowder, everyone would have called him a crank, and they'd have been right. Where would his evidence have been? And sure, they were entitled to guess or make prognostications, but should those have been taught in school as science? Should the King of France have spent millions of francs trying to invent Leibniz's bomb?
Your position is pseudoscience. This may only be for the time being, but its condition today is the issue.