One final thing: Generally, I think people make a distinction between existential risk (roughly: permanent, irreversible, and drastic loss of value of the future) and extinction risk (extinction of humans), where extinction risk is just one type of existential risk.
Here is my take on the value of extinction risk reduction, from some years ago: https://forum.effectivealtruism.org/posts/NfkEqssr7qDazTquW/the-expected-value-of-extinction-risk-reduction-is-positive
This posts also contains links to many other posts related to the topic.
Some other posts, that come to different conclusions:
https://forum.effectivealtruism.org/posts/BY8gXSpGijypbGitT/why-i-prioritize-moral-circle-expansion-over-artificial
https://forum.effectivealtruism.org/posts/RkPK8rWigSAybgGPe/a-longtermist-critique-of-the-expected-value-of-extinction-2
One final thing: Generally, I think people make a distinction between existential risk (roughly: permanent, irreversible, and drastic loss of value of the future) and extinction risk (extinction of humans), where extinction risk is just one type of existential risk.