i meeeeannnnn there are strong heroines in sfw otome too, but theyre mostly unvoiced, unless its a title that doesnt call itself otome (bustafe or jj for example). nsfw otome however, no matter how small of a budget they have, always seem to put a voiced heroine as their priority. sure, you can disable it, but why is this even an option in the first place is what i personally wonder about.
Giving my two cents (lol) but I wonder if that's less of a male-gaze problem, and more of a difference in consumer preferences in male vs. female spaces in Japanese fandom. When you look at popular doujinshi works in DLSite, most joseimuke doujin have beautiful, sexy, big-breasted heroines; on the other hand, danseimuke doujin mostly has plain, silent protagonists. To me, it seems like female audiences prefer to see themselves
through the MC, while male readers like to see themselves
as the MC; so joseimuke readers like it when the MC is an ideal type of woman they'd like to be, while danseimuke readers like it when the MC represents them as they are. And at first I thought that could be a recent development (after all, reader preferences are influenced by the spaces they're in, and those mixed preferences are popular on social media right now), but I read a bunch of ladicomi & teen love from the 1990s through the 2000s, and even old Petit Comic/Sho-Comi titles have these types of female MCs
Strong, successful MCs are also popular in Western romance books and movies, although a bit different than the ones I've seen in Japanese works. I think women are just more likely to identify to MCs without really seeing ourselves as them, since many grow up consuming male oriented media (from cartoons to movies, etc)
I'd say independent circles probably add voiced MCs in R18 otoge as an extension of that, as female consumers like the MC to be attractive, and like it when she sounds cute during h-scenes
I wonder if R18 otoge with voiced MCs also has something to do with female players also likely playing male-targeted eroge. Most otoge players aren't really into eroge titles, but the ones that like it are usually into male demographic eroge as well, so they're used to voiced female characters
I won't comment on female voices in situation audios as I'm just mildly familiar with them, but I do think it's weird to include it in those type of media, as the point of these works is seeing yourself in the story. Unless it's a plot-heavy, long series, female voices seem like a weird choice (and even in those cases, I'm not too keen on them)
I'm just blabbering though lol this is something I started thinking about when I noticed the extremely attractive MCs in doujinshi, but it's just a thought ;b I have no numbers about this "identify as the protagonist"/"through the protagonist" theory, hope it makes sense haha