Ok, and I'm not sure I understand your reply.
Let me expand on the point, and then we'll see how you respond then.
Of course it is true that evolution does not design anything. The adaptive features that organisms exhibit are a result of causation, not design or purpose. But not all evolution is adaptive. Bottle-necking, geneflow, and mutation all cause evolution that isn't necessarily going to increase the fitness of an individual or a species. What leads to adaptive evolution is natural selection, and as a biology teacher of mine pointed out, natural selection is not "selection for," it is "selection against." That is, predation and disease kill off the organisms that are less fit, and there's a small probability that the ones who are left over survived because of an accident of evolution that happened to be adaptive.
But there are a number of things that have to be true for selection to be adaptive. There has to be genetic difference among individuals. They have to have different fitness (a different phenotype), and the difference in fitness has to have been caused by the genetic difference. Only under those conditions will natural selection cause adaptation.
Now, the role of death is that death is necessary for genotype frequency to change over time, and a change in genotype frequencies in a population is necessary for evolution and adaptive change. Without death, the rate of change of genotype frequencies in a population would dramatically slow. Moreover, competition for resources might become a serious issue that itself could threaten a species with extinction. So, a slowing rate of change in genotype frequencies slows the rate of adaptive evolution and scarce resources means that a population would be vulnerable to whatever new selective force nature could throw at it: they die or even go extinct.
It's no accident that the most widespread animal phylum, arthropoda, reproduces and dies at an incredible rate. We humans try very hard to eradicate some of them and they always have some new trick for survival. The long life spans of some mammals are kind of an oddity in the animal world, but think of the stable environmental conditions that are necessary to make it possible. You could wipe out an entire generation of insects and no big whoop; do the same to humans and it takes decades to recover.
Then there are some animals that are "programmed" to die after mating, even some that are relatively intelligent, like octopus and squid. You can think of genetic change as a kind of arms race between species, and if it's advantageous to die after reproducing, then competitors that do not will be adaptively out-gunned.
