I should do more research on the subject of social attitudes toward death throughout History. I think you may be right that it helps explain a lot of our less healthy (or more controversial*) habits. It's possible though that life itself feels much more oppressive; though it most likely isn't, our subjective experiences are often extremely alienating and their purpose very abstract (compared to say, plowing fields).
The major change is your average citizen no longer sees death. Not so long ago, death was everyday occurrence. Elders or sick ones dying at home. Some of siblings dying at young age. Wars sweeping by and leaving a trail of corpses. Now people not only die less frequently, but they usually die away in hospitals.
The other change expectations of continuity. All religions have some sort of explanation for death. Whatever the explanation was, one of the reasons was to comfort people. Meanwhile today's popular explanation is void.
Of course people are scared of unknown emptiness. Both the process and what comes after that are totally unknown today, while they were rather clear not so long ago.
