Without death the world will become overpopulated and the resources that we need to survive will become depleted. Aging and death is an important/essential part of life.
If there was 1 trillion people on earth then the entire world would be like Shanghai China. People bumping into people lol we would all be living in tiny boxes stacked on more boxes
By defeat aging, I mean that therapies are developed so that humans still die from all causes still, except age related death. Most diseases are consequences of biological aging.