Anyone here seen Badlands? It reminded me why I would not care to live in a post-apocalyptic feudal society. Lacking even rudimentary social bonds of religion, common ethnicity, or both, the pomo version is a real hell for everybody without power or military skills. At least real feudalism left something in common between master and peasant, even if it was just the last judgment or common ancestors in the forests of Germany.

Some aliens show up and advise Earth that there is a great interstellar war going on and we need to get onside with them and let Earth be used as a weapons platform.

So a crew of aliens begins to construct an enormous weapons system on Earth.

It later becomes clear to Earth’s leaders that they have misunderstood the scale of things- the weapons system is the equivalent of a machine gun nest and the alien commander [roughly put in the novel] is the interstellar equivalent of a buck sergeant. [I don't know if one can be a buck sergeant in military usage, but I think that's what the author wrote and the character said]. So the alien is not able to tell them much about the war.

So that put humans in their place right there. But there was more.

It turned out that all other humanoid life in the galaxy was silicon-based, and other sentient life based more on our biology was more non-human in form. I forget the former polity — something like the Biped Alliance or something. The latter power was almost certainly the “Protoplasmic League”.

Humanity was understandably confused by where its allegiance should lie, if with either, but was being pressed to choose.

Of course the whole thing was a barely veiled analogy for the plight of less developed cultures confronted by the great wars of the 20th century. Or for that matter of countless little tribes caught up in the wars of empire these past millennia. Still fun.

I only dimly recall Alien Nation, but IIRC the aliens were both physically and mentally superior to humans but were relatively few in number and refugees from some more menacing conqueror species.

In District 9, the aliens were refugees/prisoners {?} who couldn’t even run their tech, I think.

In Gene Roddenberry’s Earth: The Final Conflict, the Taelons were super-advanced and benevolent in that sinister way aliens are when handing out goodies, and were hinted to be hiding from some worse foe.

Gordon R Dickson’s Way of the Pilgrim, a classic of occupation literature in a SF context, the Aalaag are humanity’s superiors in every possible way and are fully aware of this, and take great pains to be mysterious even to their human collaborators. Eventually it is revealed they also are afraid of something out there.

In none of these scenarios is the presence of the extraterrestrial species a unmixed benefit to humanity, or any benefit in most cases.