I guess it depends on the validity of the arguments put forth in Ernest Becker's
The Denial of Death.
The important distinction between longevity and the situation surrounding the pandemic is not the rejection of a benefit, but the construction of a fantasy that allows the rejection of the benefit by re-framing it as a detriment. The pandemic itself is recast as 'not that bad' or a 'falsification', further removing the contemplation of the immediacy of death. And with the immediate obstacle removed the subject is able to slip back into fantasies of eternity, of one kind or another, whether implicit or explicit.
Considering how most Western societies (and many others) view suicide, it seems unlikely to me that it would be considered socially acceptable for someone to choose to live half as long as they had the technical option to. Taking the average age of death as 72, would the mental health of someone who chose to die at 36 from a preventable illness not be taken into question? As with sterilization, and other medical procedures such as birth control more broadly and assisted suicide for those suffering extreme medical conditions, bodily autonomy that runs against greater social expectation is resisted.
Or, if the technology had to be administered early, would those who withhold such treatment from their children be considered guilty of child abuse? Again, in current terms, if a child suffered from a medical condition that would kill them at 36, but which was treatable, would it seem likely that the parents, in our present society, would be charged with child abuse?
It's simply a matter of sliding the mark. Cultural attitudes could (and probably would) remain the same. Our fundamental fantasies already provide the basis for and are predicated on eternities. So the reality of longevity merely slots into extant dispositions. So it may not be as revolutionary as suspected.
There would, of course, be those who rejected the technology, but most would do so, I would say, because they believe themselves to possess an alternate way into eternity, perhaps religious, or to be abducted by aliens, but the goal would be the same, whether the efficacy is up to snuff or not.