Depends whom you mean. Forsaken? Yes. Third Age Darkfriends and miscreants...eh, not so much. Also, it depends which characters you consider bad guys. I regard Siuan and Moiraine as villains to Egwene and Rand, because the protagonists' arcs involve learning to be better than them and recognizing that the New Spring heroines are sending them down paths of disaster.

It's funny that no one considers how much of Moiraine's antipathy to giving up control to Rand is due to his being male, as they absolutely would in a setting with a more conventional gender dynamic, and a male authority figure insisting he knew better than a young & inexperienced female protagonist.

At least if you subscribe to the modern weaselly redefinition of -isms to necessitate the -ist to be of a group in power.

One thing that Jordan did is look more deeply at the whole thing than most self-anointed watchdogs among the readers who go looking for sexism and misogyny and whatnot. A lot of Tumblr-fangirl type critics cite things like the treatment of the Maidens of the Spear or lack of female soldiers in the mainstream culture as examples of Real World sexism, and even evidence of Jordan's sexism, that his own unexamined gender biases were emerging in spite of his attempts to write about powerful women. Except at a very basic societal level, human physiology is going to incline a delineation of certain spheres of activity along gender lines. As society and technology develop to a point where choices can be made practicable in those areas, you can start making them more inclusive, but at WoT's stage, combat is going to be identified as a male activity. But when women are in charge, society will not VALUE male-coded activities as ours does. Hell, the lionization of soldiers and warriors is not even necessarily universal in the world. I read somewhere that one of the US's greatest mistakes in Vietnam was backing the clique of generals who overthrew and murdered Ngo Dinh Diem, because in Vietnamese culture, soldiers were not admired or respected as they were in the West, rather they were viewed as something of a necessary evil, whereas men who were seen as ascetic intellectuals and holy men were held in the highest regard. Men like Diem & Ho Chi Minh. And with Diem gone, Ho had far more stature in the average person's eyes than Thieu and his cronies.

So the Maidens and the various female soldiers in the wetlands, while marginalized in their society in the former case and subjected to disparagement in the latter, are NOT experiencing the same sexism as female warriors in other works, like, say, Brienne of Tarth. Brienne gets a lot of shit for being a woman intruding on a male activity, but to the women of WoT, that's not admirable. Instead, they are viewed as Sam Tarly is, that is, a person of the dominant gender who fails to perform a conventional gender role. The Maidens are not marginalized because they are barging into a male space, they are disdained for slumming and forgoing the superior roles to which they have access. Even Amys who misses aspects of her life as a Maiden repeats the party line, and she is established as someone who means what she says. She really does believe wedding the spear is adolescent foolishness and a diversion from more important things, even though she understands the appeal and feels it herself.

I would argue that the Original Sin analogue is Lanfear boring into the Dark One's prison, but yeah. But it's not so much a product of a less enlightened world as technological development. In the AoL, they had the means to support either gender taking up roles of reproduction or labor or sport or combat. Whereas in the Third Age, with the limitations of what is possible, a same sex couple could not have their own biological offspring, for example, nor could the physiological role a mother plays in childbirth and nursing be minimized as it could in the AoL, which for all we know could have had full-term incubators. If they can engineer Nym, they should have no problem with substitutes for a mother's breast milk. Whereas in WoT, the best the richest queen in the world can come up with is "substitute breast". There is a prejudice against male doctors, because until Damer Flinn, no man could cure you as well as a woman who could channel, and never mind that any man could apply herbs just as well as Doral Barran or Daise Congar. They'd probably faint at the idea of a male obstetrician, hell, we see Min & Melaine mocking the idea of man being involved in childbirth, through the eyes of Rand, his own successful experience notwithstanding. Because to people of the Third Age, female body parts are the sine qua non of human gestation and natal care. On the other hand, there are few people less appropriate for child birthing or care than Lanfear. Up to and including most of her fellow Forsaken. Of either sex.

Probably. Best thing to do I think would be to skip over the whole issue altogether in adaptation. It's not like anyone in the books takes a stance or makes any significant changes in sexist institutions. At best you can say there will eventually be slight course correction due to the foreshadowed prominence and acceptance of the Black Tower. Wheel of Time is a sexist setting, it is not a story about sexism.