Shadow of the DL introduces the premise; that the end is at hand, will happen soon, and there's nothing you can do to stop it. How do you want to spend the last days, I suppose?
Ok, how about this idea instead:
Starting out in a game setting, where survival and a better existence are the objective; but it's so dang hard to achieve, that the players come to realize that they won't see the pot of gold at the end of the rainbow in their own lifetimes. They will instead have to set things in motion, for their children to reap the rewards. The PCs start out playing the parents, and then end up playing the next generation into the new reality.