The idea of women being voluptuous horny beast that want to ride cock all the time is hot. But if we're basing a Matriarchy concept around it, you'd need some reason for men to dread sex and feel oppressed by women's libido. Here's my crack at it:

Women have large voluptuous bodies, and men all have disproportionately large cocks to accommodate them.They both get horny very easilly, and have super sensitive eregenous zones that feel a ton a pleasure when they meet. The difference? While women can definitely get off and satisfy their urges from riding, sucking, and/or rubbing up against these cocks specifically evolved to pleasure them. Men actually don't get any release the vast majority of the time.

Men have biological cycles. They aren't able to cum for almost the entire month. Then there's a 100 hour period called "Danger Zone", followed by a 1 hour period called "Happy Hour". A guy is able to cum during his happy hour, though he will need a woman's help to achive orgasm. However, if all the combined stimulation he received during "Danger Zone" would have been enough to make him cum, happy hour prematurely closes.

Because of these obtusely strict rules, guys are suffering from blue balls all the time. Women push for sex often, easily able to push their men's buttons and possibly even rape them. But all the pleasure they guy's get from these acts just builds and builds with no release in sight. You feel like your cock is going to explode but you just can't cross the edge.

Avoiding women like the plague still doesn't let you cum and your own libido will torture you with wet dreams and such. Your best bet at a respite from this nightmare is to make a woman so happy she'll agree to leave your cock alone and protect you during danger zone then make you cum during happy hour. But of course, that puts you completely at her mercy. She'll tease you like mad and use you as a slave. Then gets to decide the fate of your blue balls as that time of the month draws near.