It's hard to explain, it's not that they are gross but they don't feel "right" to me, I know it makes no sense. Something about them just looks and feels off. It's a similar feeling I had when I kissed a guy back in my teen years, it just felt "wrong" is the only way I can put it.
It make sense, at least for me.
It remember me a discussion I once had with my wife. Don't remember how, but once I found on the net a photo of a girl genitalia which was a real piece of art. My wife commented it with something like, "yes... but no". She recognized the effective beauty of the photography, but in the same time, being not appealed by women, she had this wrong feeling when looking at it.
I'm not sure that there's this much difference between straight and homosexual person when it come to the "not liked" genitals. A penis don't disgust me, they aren't gross or anything to my eyes (probably partly because I have one myself), but I have no doubt about it, it's not something for me.
It's same with sex toys. I had no idea where to start so our older sister got me a few toys to try out and one of them was a realistic cock and I couldn't use it. It felt wrong. We have a couple of strapons here, my partner wanted to try them so they get busted out every now and then, but they are smooth rounded ones they don't resemble a penis at all.
Once again, it make sense for me.
I have nothing against futa, even if there's interactions between male and futa. But in my mind, the futa dick is then more a living strap-on than anything else. If for a reason or another, the said futa dick is way too realistic, it stop being interesting to my eyes ; same if there's ejaculation, not because of the sperm itself, but because it's not anymore a living strap-on, but really a dick.
Obviously, in case of futa on female interactions, it don't bother me, even if the MC is initially the girl. For this scene I'll mentally switch and become the futa, so the one with the dick I have in real life.
I would probably be okay with something that resembled an elongated clit. I have never met anyone with both sets of genitalia so can only go off pictures. Without trying to offend anyone the genitals look weird but I wouldn't know if they put me off without seeing them in person.
So, if I understand you, it all depend of how it feel in your mind. In a way, it's more or less like what I said above about futa dick being living strap-on. If you feel it like a "weird clit", it would perhaps be ok, but if you feel it like a dick, it's surely out of question.
Anyway, thanks for your answer.