The way people justify gynocentrism is with the fact that each man can impregnate a large number of women whereas each woman can only be impregnated by one man per 9 months, so a society's fertility is bottlenecked by its number of women. A tribe of ten women and one man will have ten times the fertility of a tribe of ten men and one woman.

All this is completely biologically correct, but Western society is, in theory, monogamous. In a strictly monogamous society that has more women than men, the excess women won't get to reproduce because each man is only allowed one woman. Hence, the aforementioned argument to defend gynocentrism doesn't apply. In strictly monogamous societies, men and women have equal reproductive value.