Infectious diseases have ceased to be a major threat. Food can easily be bought in sufficient quantities down in the supermarket. Evolution, on the other hand, is something that occurs in the tough wilderness environment, where every day is a struggle just to survive. So the modern easy environment has caused evolution to stop. Unfortunately this understanding of evolution is a bit wrong.
Evolution occurs whenever different genes can result in different rates of reproductive success.
Modern civilisation has not eliminated natural selection. It has changed to some extent what is being selected for. If modern medicine can protect us against infectious disease, then our own bodily defenses are less relevant, and indeed may become an unnecessary expense. If people can choose not to have babies even while having sex, this may reduce selection for genes that determine sexual desire, but it will increase selection for genes that cause people to consciously want more children. In fact, since evolution tends to track the environment, it is when the environment changes a lot that evolution goes faster, since there will be more changes that can result in immediately better adaptation to the new environment.