That's fair to ask, don't worry!
I won't talk about All of it because some of it really is just my own personal upbringing to me specifically and my own life that probably shouldn't be aired too publicly on a public twitter account, but I can talk about half of it. Thank you for approaching respectfully and not calling me a slur lmfao. (Had a previous ask call me one earlier today.)

I'd like to once again state this is my personal views, I think some people will be the way they are. I don't really see my mind changing on this subject and I'm aware many others won't change as well.

For some of it, a lot of WxS familial stuff tends to just be tied deeply within shipping discourse. I don't like that at all and a lot of the ones I've seen related to WxS are often in that same vein where people will call whatever pairings they're not big on familial as a sort of "gotcha". I've been in this fandom for a very long time (over 3 years) and I've seen people sent death threats, rape threats, and various insults to others over not liking WxS familial stuff. Last year in particular a friend of mine was harassed for being an "incest shipper" because they liked Nenekasa. People cited Childish War, a cover where it's pretty blatant they're... narrating a play. Nene starts off the script introducing it, and the two join in only when it's convenient in the 3DMV (which is basically why the line dist is kindof awkward, lol.) This stuff bothers me and as such, it's developed a "bad association" to begin with.

More importantly to the HC themselves, I think it's just such a strange way of seeing WxS's dynamics. I guess I could accept "the whole unit" as a found family sort of thing with four weirdos who found a place in each other, but individually any dynamic being seen as familial rubs me the wrong way.
I think an important part of WxS's stories is their very own canonical familial dynamics. Tsukasa has Saki and Toya and how he wants to be a reliable older brother as a core part of his character, something he doesn't shut up about. It's what his FES card is based on for god's sake :sob: Tsukasa seeing Saki and Toya as part of his family is such a crux of his character that adding anyone else just feels deeply wrong to me in a way I don't like.
Emu's relationship with her family has been drilled in with the story over and over just like Tsukasa. Her grandfather who she mourns and respects drives her story, her siblings who each have their own relations with Emu and the way they bond with her. Keisuke is a bit partial to Emu and lenient, Shosuke is a bit of a tsundere, and Hinata is gentle and reassuring. Emu treasures all of them greatly.
I've seen some occasional people cite stuff like Emu saying Tsukasa is like her grandfather (end of ch8 PIMH), but it's about how the two have the same dream--for everyone around the world to smile. Toya does something similar (WED1 ch6) where he compares Rui's way of thinking of "giving no quarter and taking no compromise" to his father, but does anyone actually see Rui and Toya familial? Maybe someone out there does, but I've never seen it.
For Nene and Rui, I think the fact they're only children and don't have a type of sibling connection adds to their character as well.
In story, it's pretty reiterated whenever the topic of "family" comes up (usually prompted by Emu of course) that they're all separate and have lived different in every sense. Everyone has their own family.
I'd like to add that the Nene and Rui's middle birthday is intentionally Tanabata, a Japanese holiday about two lovers who were forced apart for a time period and are able to reunite... sound familiar?
Basically, I think the way the familial dynamics contribute to the game sortof makes it often... bizarre to alter them. It doesn't really fit these characters stories or dynamics. It often makes some of their canon strange, and I'm someone who reads every story in the game and thinks very deeply and fondly of these characters.

Once again, a final time this is my personal views, and thank you for being respectful once more. Have a nice day!