The body forms structures over the course of development. But I don’t think it can replay those actions again. In places like the knee and eye lens, the cells that formed those structures did their job and dissolved their nuclei. I’m more familiar with the eye lens example so let’s go with that. The cells there are just bags of proteins and antioxidants. No nuclei, no mitochondria, no activity. Oxidation from the environment gradually damages those proteins and lead to cataracts. Everyone would eventually get cataracts if they could live forever.

DNA is not enough. There was coordination in time and space to construct the body during development, and the growing body has no damaged cells and structures to deal with.