It seems absurd to argue that death is necessary or good when there is exactly zero experience with the alternative.

Imagine a society where everyone has a ball and chain permanently attached from birth. It would be just a part of life. Some thinkers might write articles about how much better things would be if a way could be found to get rid of the ball and chain. Others would come up with arguments for why the ball and chain is actually good, or even necessary. The limitation on movement gives life a purpose. The resistance helps build strength.

Looking at such a society from the outside, we'd find the latter arguments ludicrous. How can it possibly be better to stuck with a major physical restriction your entire life? If anyone said we should start doing this to all our children, they'd be run out of town.

If humanity does solve the problem of death, I doubt it will be absolute, in any case. Aging might be stopped, maybe added resistance to disease and injury, but nothing is going to allow you to survive hugging a detonating nuclear bomb, or any number of other physically extreme events. If you decide forever is not for you, then you'd be able to make that choice.