This new Fire Emblem Fates is in no way bad or disgusting. It's merely different than the others. You guys are willing to let down an entire game for a tiny detail you don't like? You don't have to S-Supports your siblings. Though, I do admit, being the given the ability is gross to me...
Is this whole incest deal the only reason you guys don't like this game? Overall, the mechanics and gameplay features have only improved since Awakening, and I feel Nintendo is making a good decision with this. Face-rubbing, that's not me, but it can appeal to other people.
And there are people out there who (as weird as it may sound to you) actually do like this feature to marry siblings.
There's a good number of reasons I don't like this game:
Being better than awakening does not mean it's good. Awakening was completely gutted in terms of combat and map design compared to previous games. It was a very shallow experience overall and the character writing was about as thin as chicken broth given every character had to be generic enough to be able to marry every other unit of the opposite gender. This game has almost certainly not improved in terms of writing for just that reason same reason.
Six of the game's character designs are straight up recycled from awakening which is god damned lazy. Transparently so too, given they're all Nohr exclusive as a means of selling the newcomers to the series who are worse players on buying the 'harder' story path. This is exceptionally bad imo because the game's roster is actually rather small overall not counting in child units being a mere 19 or so units per side.
'Skin Shipping' is weird.
A lot of the 'new features' are actually just re-introduced. Lack of weapon durability, jail, and the my base feature all come to mind. (Gaiden, Thracia, and Gaiden respectively)
Incest is gross and so is being able to marry (and have children with) underaged units. Pedophelia isn't cool and incest is also not cool. And to be honest, yeah this alone is enough for me to drop the game especially after how disappointed I was with awakening.
Overall I haven't heard or seen anything about the game that made me particularly excited in the first place, and a bunch of the stuff I have heard only made me less and less wanting the game to the point where now I just straight up will refuse to buy it.
Edit:
People who want to marry their siblings are gross, that's really all there is to it. Making a product that panders to an audience like that ought to tell you of the general quaity of said product.