A “Yamato Nadeshiko” is defined as the traditional ideal Japanese woman. These qualities include being loyal to their husband, putting family first, modesty, and being skilled in domestic matters. Belldandy from Ah! My Goddess is a prominent example in anime and manga of a Yamato Nadeshiko, and the fact that Ah! My Goddess has continued to run for many years indicates that this type of character is relatively popular today.
Of course, the spotlight in recent years has been on moe characters, and while some character traits reinforce the idea of the Yamato Nadeshiko, others defy them. Key’s heroine of heroines Tsukimiya Ayu has loyalty as one of her important traits, but is also a clumsy tomboy whose cooking ability is on par with Homer Simpson pouring cereal. Tsundere characters such as Hiiragi Kagami are strong, capable, and put family and friends first, but are independent-minded and are anything but submissive. Aisaka Taiga from Toradora! meanwhile is a clumsy tsundere.
I don’t think the intentional increase of moe traits in characters is, at the very least on a basic level, “progressive feminism,” but I think it’s worth taking a look at how these characters relate to a concept with a long history in the society from which their fictional media are produced. In American fiction, particularly television and movies, there are certain stereotypes for female characters, particularly when it comes to romantic interests. The Girl Next Door can be considered a reaction to the Bombshell (or vice versa). Any time there’s a shy girl who turns out to be highly sexual, it’s actually just a simplified form of “what you see isn’t always what you get.” Though they are now recurring, even stereotypical concepts in fiction, their basis is in the trends of what most people want in their entertainment, at least as it pertains to female characters.
Granted, otaku are not “most people” in Japan or any other country in which they (or should I say we) reside. And when non-typical people look at something typical, I think there’s often a desire for something “different,” though perhaps not drastically so. But the line between “different enough” and “too different” is a very personal thing, and I think it’s the area in which disagreements regarding the validity of moe characters arises.