My question is -- has it always been like this? Or somewhere, way back when, did some group of magical women do something that caused the men to kill them off and instigate a ban on female magic use, a ban that then translated over the decades/centuries into a complete and insistent belief in the physical inability of women to use magic?

the latter!! it might also be cool if there's this like rogue group of women who still use magic, and your main character found them. though that might not work in the context of your story......??

it sounds fun! i actually have some questions for you about writing/wanting to be a writer if you don't mind :) i've finally come back to writing fiction, but i have a lot of doubts and questions.... and you were the first writer person that popped into my head :)