> In other words, that’s more of a religious rather than scientific hypothesis.

I get what you're getting at, but I don't think it's so clear cut. Religion is more about organizational beliefs than just beliefs. Many parts of science are pretty far fetched in terms of us only knowing a bit with a very tightly constrained perspective (humans sitting on Earth with limited technology in the Solar System in the Milky Way) but making leaping conjectures. So in fact, science and religion have some shared analogues. (C.f. Paul Feyerabend.)

Certainly, the hypothesis you replied to is incredibly far fetched. But I don't think it's religious. It's more fantasy.

It's not falsifiable, therefore not scientific

To be clear, I didn't say it was scientific.

TBF we are assuming that we universally know what toolness looks like. There easily could be other forms of or paths to technology that we are completely ignorant of, even to the point of being ignorant of our ignorance.

A much less out-there version was in Star Trek, they built spaceships and left, bringing most/all of their civilization with them. That version was just treated as lost history, with whatever may have been left behind simply not having been found yet or having decayed over such a long time period.