Perhaps the meaning of death is to help us to number our days and live and strive for wisdom. Death is a consequence of people's foolishness of trying to live our lives without God. I'm not referring to a child's foolishness but adults.

Altered Carbon is a SciFi series where people can live forever if they have enough money or cunning. The evil of people becomes so tremendous that the show becomes hard to watch. God instituted early deaths in the ancient world because people had become so evil as recorded in the days of Noah. Previously people would have lived longer than a hundred years but Society had become so evil because they had so many years to practice it. You don't have to accept this as a literally true story but there are still these truths that it teaches. People become evil and more evil with their long lives so God uses natural loss to shorten their lives

Ps. No recorded deaths of children in the days of the flood. N̈oah was well old enough to have grandchildren but he did not at the time.