I think you need to be careful with the word "want". It's not terribly useful to think of desire as separate from choice. Instead, think of "of the choices X, Y, and Z, which do you choose".

Frames this way, retiree behavior makes sense. The choice they're making isn't "death VS eternal youth", the choice they're making is "spend my remaining time worried and unhappy VS spend my remaining time calm and relaxed". They may or may not consider the choice of "increase my remaining time a little bit by changing in uncomfortable ways", but even if they do, it's hard to argue they're horribly wrong.

Almost nobody (including Clarity) chooses the bundle of reality that includes short-term pain and a large chance of immediate death with a small chance of reduced quality of ongoing life.

IMO, the way to convert deathists is not to. Just outlive them.