Earlier quoted context omitted.
I think it's the exact opposite. The day being old is no longer a disease and a path to inevitable death will be one of the greatest things to ever happen to humanity, now and forever into the future. Especially if you can retain a youthful, healthy brain and body no matter how old you are. An old tyrannical movie villain dies and a to-be old tyrannical movie villain is born. Billions of people shouldn't be sentenced…
Pretty sure the possible world being lamented in the GP comment is not "everyone gets to live forever and stay healthy and youthful" but instead "there exist expensive, parasitic procedures which will allow some rich people to have drastically extended lifespans."
You can be almost sure that once the underlying mechanism is known, the necessary stuff will be synthetised instead of being transferred from a young person to an older one. If only to guarantee stable supply, consistent quality and rule out accidental transmission of various pathogens from the donor.