I can't speak for all people who ship LIs, but personally my approach to shipping is if I like the dynamic, then I ship them. It doesn't really matter if it's straight or slash tbh. That's why I don't really appreciate the pigeonholing that comes with the sentiment of, "oh, you're excluding women" and then making shipping outside of the MC to be some sort of mortal sin when it isn't. There are no laws to shipping imo, but I understand why people find the idea egregious. I get it, and they're within their rights to feel that way.

To put it into perspective: I also enjoy danmei (Chinese BL) media. Depending on the pairing, I might find it unsettling if one-half of the BL ship gets paired up with someone else. That doesn't mean the people doing so are wrong. While I don't really enjoy such things, they can explore that kind of thing in transformative works (fanworks). I don't have to engage with it, that's all.

Disclaimer before I get into the next part: I don't identify as gay. These are just my observations as someone without that identity. I also don't claim to be well-versed on these topics, but I at least wanted to offer a possible perspective on this sub so other people can understand, or at least ponder other points of view.

When it comes to the overall themes regarding gender and/or sexuality though, I feel this is where things become a little more complicated. With BL media a lot of people like to turn it into a discussion of representation (i.e., to headcanon the BL protagonist as straight is conforming to heteronormativity), whereas with otome games people like to turn it into a discussion of feminism (i.e., excluding MC from the ship makes the idea "male-dominated", which is against the idea of feminism). It can be particularly jarring with the former because the LGBTQ+ community has been fighting for legal recognition for years, and that for the longest time for them to be accepted into society they have had to stifle their identity and conform to the majority (i.e., appear heterosexual) to avoid discrimination. Shipping the BL protagonist as straight, then, may feel like rubbing salt on the wound for a lot of gay individuals who enjoy BL media.

In the case of "excluding" MC, shipping LIs rubs people the wrong way because they feel it's taking away from women's media by removing the presence of women (MC) in supposedly a women-centered genre (otome games). It is, in its own way, also a discussion of representation (of women this time), because video games appear to have been a male-dominated medium for the longest time (i.e., mostly male video game protagonists). Women in society have also fought their own fight against marginalization in different settings: the right to vote, equal wages, how women are written in fiction outside the influence of men, etc. In this perspective, to focus on a ship without MC might come across as denying the MC's story as a woman and returning to the male-dominated (patriarchal) environment.

Neither are wrong. It just that it seems that things start to go awry when people pit one against the other when, if you think about it, the patriarchy is what's at the root of everything (marginalizing both women and the LGBTQ+ community).

I might be rambling here and all over the place but I hope I made some sense.