This is a generalization, I know, but in my experience people with a firm belief either in a hereafter or the complete opposite, that this is the only life we get, find it easier to accept that life must end.
However, few of us, if any, like the thought. Certainly, those who are terminally ill usually come to accept that their death is approaching and may even come to welcome it if they are in pain, or tired of the treatment necessary to prolong their life.
The very old can reach a point where they feel life has nothing more to offer them.
None of this really answers your question, though.
IMO death is a tabooed subject because people are afraid of it. It is surely natural for healthy, happy people to dislike the thought of death- their own or others. However, refusing to speak of it, makes the taboo even stronger.
I am in no hurry to die, and like many of you, occasionally worry about how difficult it may be to live the last months of life, but we none of us know what the future holds. Not everyone dies a lingering or painful death.
The older I get, the more I realise that it makes no sense to be afraid of something that will assuredly happen, any more than it makes sense to be afraid of thunderstorms. Death will come, but may well come in a form and at a time that makes it welcome, not horrific.
Comforting the bereaved: the worst you can say is nothing. If you don't know what to say, say exactly that. You are thus telling the bereaved person that you sympathise and probably expressing more or less their own feelings. If they want or need to talk, they can do so, which they can't nearly as well to someone who has basically ignored the fact that there has just been a death of someone close to them.
The emotional spouse or child: "Oh don't talk about it, I don't want to think of it." Very well, but it is easier to discuss while we are still all hale and hearty, rather than when one of us is , might be or fears he or she is dying! If they will not discuss it, sit down now, whilst you are well and write them a letter.
It is hard to do, I have done it, so I know. It did, however, console me that I had made an effort to tell them both some practical things and that I loved them. When it turned out that was I was dealing with was NOT cancer, i destroyed the letters, hoping that at least some things will be different next time I am afraid that my departure has been announced.
Perhaps discussing death here will make it easeir to discuss it elsewhere.
Whether we like it or not, it is part of life, We were born, as the Book of Common Prayer puts it, not of our own volition or of any man's but of God's - whether you believe that or not, there is no balking the fact that because we have been born we will assuredly die. Time to re-read Hamlet?
Time to enjoy life and to try and think sensibly about the ending of it.