We had multiple loses in the past few years. One was a longer struggle. However, it wasn't torture the whole time. I admit, some days were pretty bad, but there were also good days. And there were also joyful new experiences, like meeting newly born family members. Thing is that while quality of life may look terrible from healthy persons perspective, body adapts to that state and combined together with moderen pain medication person is not in constant physical pain. Point being that it's usually not constant physical torture for years until person dies.
Another issue is psychological pain. This is where we can make a difference. Allowing people to not be perfect or the best, but still be equally worthy can do wonders.
> whether life is worth living should be primarily decided by the liver of that life
I find it that people can have quite significant change of heart. And it is not rare at all to have one.
I'm not sure if the unwarranted killing of a person is worse than permitting their torture for months or years on end. I also don't know if that answer changes if for every 1 person who would be killed in an undesirable way that we had to torture 1000 people for an average of 6 months to avoid it.
That's the essence of this debate and it will never find an objective answer that will satisfy all, which is why I default to allowing people to choose, even if some will choose in a way that I would not. (After watching two of our beloved elderly family members struggle for many years and watching another two struggle for weeks in one case and months in the other, our family has expressed our thoughts to each other. We're not universally in agreement, but I'll support each of them in their choices.)