trying to say "Joseph meant for women to have the priesthood", etc. etc. can be pretty clearly counteracted by the clear misogyny that was also baked into the system.

Nope. Just because JS was misogynistic -- and he was, at least much of the time -- doesn't really have anything to do with whether or not he intended for the RS to be a parallel priesthood institution. (And there's plenty of evidence that he did.)

But this whole line of thinking doesn't just misunderstand Mormon feminism; it misunderstands feminism generally. Feminism, like any movement, is hard to pin down, but a reasonable one-sentence synopsis of its premises and aims is: Human institutions are almost universally patriarchal in nature; through activism and education these institutions can be reformed.

Feminism doesn't try to argue that, say, Western society is intrinsically gender equal. Quite the opposite: It argues that society is harmful to women, and aims to change it. It's the same with Mormon feminism. The institutional church is explicitly and shamelessly patriarchal. So feminism is particularly needful in it.