[epistemic status: trying on a model, unsure if "belief" is an applicable word here]
I don't think the counterargument works, but I also don't think there's an argument that works either. Death is neither bad nor good, it's just a part of the world which has formed our ideas of identity and experience. Certainly, on the margin, I'd prefer to delay my own death, and more importantly my decay in body and mind that will likely precede such a death.
I don't actually have strong intuitions of whether I'd prefer others' immortality, over the somewhat dynamic system of death and replenishment we've always had so far. Details matter so much that I don't think a far-mode general value can be applied. I don't even have a systemic description of individual vs collective identity and utility that would inform such an intuition.
I can get behind any movement to defer or remove the effects of aging, but my value drive there is to increase total maximally-valuable experience-hours, not to privilege any existing individual over a potential one.
suffering as qualia of pain is technologically simpler
I can't tell if you're serious here - it seems to negate your argument (because we haven't actually done so or taken significant steps toward it) if this is an intentional strawman, but it's pretty weak as a motte-and-bailey.
I didn't say "pain", I said "suffering". This includes the anguish that one has degraded over time and is now a net drain on family/society. And the degradation itself, regardless of the emotional reaction. Once you've solved aging, then there can be a reaso... (read more)
All the usually offered counterarguments to the idea that death is evil boil down to one universal counterargument:
If there is no death, then there will be a bad phenomenon X (overpopulation, cessation of progress, eternal dictatorship, boredom), therefore, death is necessary.
However, this universal counterargument does not work:
For example, if at the birth, each person is granted so many resources that it will be possible to provide her with resources for entire endless life, then overpopulation will cease to be a problem. Overpopulation is only a problem because of the clash between the idea of finite resources and the prospect of exponential proliferation.
The counterargument also does not work because it is not central. The negative X phenomenon can persist even if death continues. Lack of progress, eternal dictatorship, overpopulation and degradation are possible in societies where people have short life expectancy.