they must be large enough to house DNA, proteins and structures needed to survive and reproduce but remain small enough to allow surface-to-volume ratio that will allow adequate exchange with the environment
Viruses are not alive. Although they sort of “hack” a host’s cells and reproduce, they do not breathe or move on their own. A virus will sit on a counter forever if it’s untouched. Viruses are spread by physical contact, not because they can move around on their own.
Although viruses can attack and hack, and use your cells to reproduce, they are programmed to do so.
Cells are very much alive, while viruses are not.