If his argument is accepted, then the feminist task becomes the extermination of culture and replace it with some other phenomena. Obviously, this is a questionable implication. Therefore, Rubin argues against L-S on this point. She does not see the exchange of women as a definition of culture or a system in itself. It is simply part of the social relations of sex and gender.
Kinship systems do more than exchange women, they are systems of relationships.
A kinship system based on the exchange of women is one in which women do not have full rights in themselves, men have certain rights over them. Deeper into the Labyrinth L-S goes on to analyze the sexual division of labor. It is a taboo against men and women being the same, therefore it creates gender by dividing the sexes into two mutually exclusive categories. The kinship system is about marriage and marriage presupposes gender, a socially imposed division of the sexes. For instance, although men and women are different on average, there is quite a bit of overlap in variation.