Death is simply the next step in our journey through this universe. I think so many are scared of death not so much because they are scared of death, but because they are scared of the unknown. As you've written above our ancestors had no uncertainties regarding death. They knew that when they die they would go Valhalla or Hel to see those who had died before them. No uncertainty and nothing to fear. Today many people have no real belief. They question everything, which is good in some ways, but in the case of death it is not so good.
As I get older death is not something I fear, but it is not something I welcome either. I realize it comes for us all, and simply wish to enjoy my time here with my family and friends before moving on to the next phase of my existence.