The problem is partly that some people just do not like other dick/pussy shown without the MC active, especially when a main girl. Whether in past, present and future and if she is meant to be in an emotional relation she qualifies for NTR, even if she is the sister and they will never have a romantic relation. LI is way broader defined as being in a relation with when comes to NTR genre.
Problem is though there is no other tag as NTR for other dick/pussy so the three letter word comes up way too often even if the taking away or jealousy aspects do not play a role in game, then again the trope that all other males are even bigger assholes as MC does tend to make those NPC's not to be people you want around your women in the first place even without sex involved. Problem partly with that is people tend to get into a hair splitting discussion what NTR is, while the dislike is for some elements of that genre which are in game, whether it is NTR or not.
Considering lesbian, well a lot more people do not enjoy it or do not care about it as seems to be expected especially in a male MC oriented game where people want MC to have the action and not two women. For that you have female protagonist games where it makes all the sense a female protagonist has the action and not two males together without her that are being wooed by her.
The fact every game for some reason has to put it front and center even in games where there is no harem path to at least make it somewhat more believable a harem path would work with all women being enthusiastically bisexual does not help. It is getting old by now and somewhat irritating to have it shoved in every game whether it fits or not.
Well in this game at least it does make some sense with the big disparity between numbers of males and females in game so I will personally just skip over those scenes since to me they are just not hot in the first place.