In addition to all humans being destroyed, the only other living thing we see in the story dies because it cannot reach the food it smells. So, not only did technology destroy humanity in the form of a nuclear bomb, but it also almost cruelly keeps the dog shut out of the kitchen, unable to access the food that the kitchen was still constantly cooking. The house itself does a better job of protecting what's inside than humans ever could; since the house is still standing, one may assume that the people would have lived had they been indoors instead of out.
That is where the true frailty of human life lies. All that's left of those who once seemed so vibrant are shadows on the wall. The force of the blast literally captured their silhouettes at the moment of immolation. It's almost as though the people are a part of the house now, or as though the house has somehow absorbed their life force. Of course, one can argue that since humans invented the technology, they are still alive and well while it remains working.
At least in this story, the power of technology is written as a much more significant and lasting force in the world than the fragile human life that created it. The story's characters are entirely robotic or technological--we have the robot voice speaking to the absent family, the scurrying techno-mice that clean the place, the breakfast and dinner making machines, etc. All of these pieces of technology were, long after the family was, alive and well in a world that most of humanity had been destroyed.
It was technology itself that destroyed the fragile human and animal life that existed on the planet; after the blasts, technology was the only thing that survived, at least for a while. The humans in the story are completely wiped out, but their home functions without them. So, the frailty of human life is pretty evident in the story, as being powerless against the force of technology. I hope that those thoughts help a bit; good luck!