Who are you to judge whether someone who has lived for over seven decades should go on living or not? If they feel their life is done, have nothing left to live for, and fear degenerating into a husk of their former selves (dementia) stuck inside a broken brain for as long as their body holds out, than why should they hang on?

It's arrogant and selfish to force people to live on for as long as doctors can keep their body alive. No euthanasia just means more messy suicides.