Thee wouldn't be a demise, it would just be a different kind of society. Males are expendable for most of society, in earlier centuries, they would die from warfare, diseases, working in high risk professions and so on. The current society we are in where we expect or desire pair bonding for life with an exclusive mate is rather new and unstable. Lost of women would be quite fine with a harem like system where they share a high quality mate with other women and now that women earn on par with men they are not limited by the male's resources being shared between children by other women.
