What advantages might sameness yield for present-day society?
Most of the advantages that "sameness" might yield for present day society are not really advantages at all when we look closely at them. But if we were all the same, we would not have competition or jealousy, and we might not suffer depression and despair when we feel we are not measuring up. These may seem like positive social conditions, but they would come at great price--life's infinite variety.
The aspects of The Giver that reinforce sameness have to do with the Assignment (of life choices and career) and the family. All families "are allotted two children, one male and one female" (from e-notes), and the sameness of the society brings a bland kind of peacefulness to the society. But, of course, another aspect of sameness is that no illness or disfigurement is allowed, and the peaceful sameness of the novel comes at great cost, as Jonas learns.
If our present day were to have the same kind of sameness, we might eliminate some strife and competition, but, as in the society of The Giver, some people might need to be killed in order for the society to achieve "sameness." There is no advantage that could compensate for the sacrifice of human life.