Why the focus on immortality? I don't want to be immortal but I'd take a few thousand years.

That aside, I think longevity-skepticism is still mostly adaptive. I haven't seen any concrete progress and the people who are true believers are a. getting their hopes up and b. tend to be really gullible/easy to manipulate. We should ideally be skeptical enough to avoid those traps but hopeful enough to pursue genuinely promising research.