There are a couple of things that make death bearable. Any longevity treatment should placate the first and we should aim to compensate the second with plenty of change in our lives.

First is physical ailments. Even a healthy person will accumulate aches, and those will slowly erode they will to live. Several of my grandparents (and some that were not mine) have expressed that they were waiting to be taken, and I'd wager that would be a part.

Second is the mental fatigue. Not only your mental state is akin to your physical one, so you might be mentally exhausted, but also you begin to get bored with most media. It's hard to find a story that hasn't been told before, music that you find original and good, few dishes that you still dare to discover, ... .

Apart from the personal point of view there's also the general one. There two more problem arise.

Sustainability, as the planet can support what it can. The society and the way resources are managed will have to change a lot if people live longer. But don't worry because...

Power. You'd go from families holding power to individuals. No longer the young master will spend all the money and none will be left, because their parents will have control over that. Situation could become even more oppressive with them withholding the longevity treatments, giving some to their employees and none to the general public.

So while I agree with your sentiment, which is also beautifully expressed in HPNOR, I'd say that there's a lot of transformations to be made before it's good.