The Tithonus Error is one of the learned patterns by which people reject life extension out of hand: from roots in childhood and education and stories, a majority of people come to believe that extending life means making people older for longer. Most people have an entirely justified horror of the later stages of degenerative aging, and so the idea of more of that just isn't on the table. The rejection of more life under those terms is instinctive and visceral.
This rejection is based on a false premise, however, and all that rational fear of aging is piled atop a single irrational misunderstanding. The goal of all medicine, and especially longevity science, is to enable people to be younger for longer, not older for longer. Aging is nothing but damage, and longevity therapies will be no more than ways to slow, or for preference repair, the accumulation of that damage. A machine with less damage is a machine that works better for longer, not a machine that lingers on its dying gasp for longer.
That rational fear of aging is big and powerful, however, and it's been somewhat hard to fight one's way past it to point out that "older for longer" just isn't going to happen. See these rather depressing studies for example:
The wish to die had either been triggered suddenly after traumatic life events or had developed gradually after a life full of adversity, as a consequence of aging or illness, or after recurring depression. The respondents were in a situation they considered unacceptable, yet they felt they had no control to change their situation and thus progressively "gave up" trying. Recurring themes included being widowed, feeling lonely, being a victim, being dependent, and wanting to be useful. Developing thoughts about death as a positive thing or a release from problems seemed to them like a way to reclaim control.
Aging takes everything from us in the end, piece by piece, and eventually even our desires and our will to live crumble in the face of physical and mental decay. Younger people understand that this lies in their future, and most believe that it is a certainty, unavoidable. They've seen what happens to older relatives, they read, and they learn - they base their expectations of the future on what they were taught by experience and observation. It doesn't matter that the pace of chance in technology will render much of that obsolete and useless in decades to come; it's still the case that people, in a deep-seated way, expect to live a life similar to that their parents and grandparents lived.
The prospects for medical technology offer much, much more than that - but the medical control of aging and defeat of all disease is an opportunity to be seized rather than a certainty already in the bag for those people in middle age today. Rejuvenation biotechnologies may or may not happen in time for us. I'd say most likely not if a supermajority of people keep their heads stuck in the sand of the Tithonus Error, refuse to think seriously about aging and medicine, and refuse to do anything constructive to help speed research and development. Things only tend to happen with speed and certainty when there are large communities of supporters: millions of people demanding progress and pitching in to help in their own small ways, enabling scientific communities of tens of thousands and billions of dollars of investment in the cutting edge of research.
We see that in fields like regenerative medicine. We don't see it yet for longevity science. That must change if we are to expect similar degrees of progress towards therapies in the years ahead.