All of literature can be regarded as an "old boys club" if you squint, but it's not like she'd have been unique. "The Left Hand of Darkness" was published before I was born, but I was old enough to read "The Handmaid's Tale" by the time that was published, albeit not quite old enough to properly understand it.

In fact I don't think "The Handmaid's Tale" really makes sense without the context of the AP feminists. Gilead comes about, as I understand it, because the AP feminists think they can use the Religious Right to achieve their goals and unsurprisingly that goes badly for them. AP feminism doesn't even exist when "Left Hand" was published.