Indeed when I 1st heard that line of the book with Witchcraft and the connection to Womanhood I got allot what James Robinson was going for.
The main point was the factor of real world beliefs, not just witchcraft but other beliefs that center around the natural world, nature and the focus in Women mainly around the factors of Women being able to give birth to children. This struck me on many levels since this is longtime history I learned about over the years hearing about it and really seeing it being put into a book the makes so much sense in using it really gives me a much better appreciation for the book. Even Me being a Male and a Roman Catholic, I can appreciate and get interested in these themes and the core of them being in real world beliefs based on nature that is firm in both history and still is believed in today.
For Wanda Maximoff the core of this belief, the ideals of Womanhood and with that nature/mother earth works So Very Well with her on many levels. Why Wanda now more than many other Great Women heroes is that the Beliefs are based on Witchcraft as one of the beliefs and with Wanda having training in being a witch no one else is better for it beside Agatha. Also, Wanda has always been a Very Feminine Lady, many Lady heroes are but for Wanda to have extra focus on this cause it has been a central theme towards her character since the 1960s is good in going hand-n-hand with her persona. It is good to to show that not only can these root personas break free of what might have been at the time like
Saffron said, more at the time gender roles for Women and Robinson can do a 180 on it to turn it into a Major Strength!
Even though Wanda was already strong to bat with this creation in the Silver Age, a way to evolve it to break Many More Glass Ceilings is just Epic and Warming to see done in such a clever way.
Also, Robinson DID mention in an Article that Wanda Maximoff being both a Witch and a Women will have skills and connections to abilities that Dr. Strange just will not have because of that. THIS will make Wanda much more of the Expert to go in these fields and make her a Powerhouse in her own right in the ANAD Age of Marvel! What I like about this is it just not only makes Wanda More Unique, but it helps to separate the powers of Magic in the Marvel Universe so that it is more based in Variations and not just mostly under one Master like Dr. Strange that knows how to command most of it, and leads to a specialist style of power sharing, Love that Idea Allot Indeed!