To some degree I agree with your last point. Before the idea of aliens, writers like Plato and Thomas Moore would posit some undiscovered island where they coul

To some degree I agree with your last point. Before the idea of aliens, writers like Plato and Thomas Moore would posit some undiscovered island where they could imagine a culture unlike their own existing, which like with aliens, gave plausibility as to why that culture would have a different history and traditions than their own. Of course they, like many speculative writers today, were really writing about how they wished their own society worked.