There's another part of this too (because I was in anime fandom from about 1997 to 2002 or so, and so saw the beginning of what you're talking about. I remember Gundam Wing fandom, which had every issue you mention and then some.)
The "Japanese men are so pretty" fail is partly because teen girls are scared of sex and sexuality and so are honestly a little freaked by men who play up their secondary sexual characteristics. I can remember talking about how body hair is "gross" with my friends early in high school. Japanese idols and the men in anime and manga tend to be portrayed or to portray themselves as more androgynous, even in shounen. That makes them a whole hell of a lot less threatening to teen girls than the men in Western fandoms who are usually at least 30 years old.
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The "Japanese men are so pretty" fail is partly because teen girls are scared of sex and sexuality and so are honestly a little freaked by men who play up their secondary sexual characteristics. I can remember talking about how body hair is "gross" with my friends early in high school. Japanese idols and the men in anime and manga tend to be portrayed or to portray themselves as more androgynous, even in shounen. That makes them a whole hell of a lot less threatening to teen girls than the men in Western fandoms who are usually at least 30 years old.