I think we can. What about this plot: The decline of intergroup norms partly due to the decline of Christianity and partly due to SJW insanity finally led to a genocidal worldwide race war which caused all tribes capable of producing WMDs to destroy each other using nukes, ethnic biological weapons, military drones etc.

Only Sub-Saharan Africans, Australoids, Pacific Islanders etc continued to exist. Civilization completely collapsed, starvation and cannibalism were widespread and diseases such as Ebola got out of control. Survivors rapidly declined to Medieval or even earlier tech and never recovered.

When aliens arrived at Planet Earth or when some mutant non-human species in the nuked world developed civilization they wiped out the remaining humans and did not even believe that human civilization had ever existed.

Moral of the story: Do not become a sociopathic defector for humanity is more fragile than what we think we are.