I find it funny how often labels like Ntr are followed by "avoidable", oh it's avoidable, don't worry... but stuff like incest is totally okay.
To explain that to you
Incest = Very popular by the taboo of it. Like a forbidden fruit its sweet and delicious because it is forbidden and most of the time it involves love, something all humans search for in their lifespan. It does NOT mean that people who like Incest would want to fuck their own family members.
So Incest = a Fantasy that people like to outlive in their head with stimuli in form of pictures or porn. You can compare it to the rape fantasy most women have. No women on this earth would like to get raped in real life but the fantasy with a partner she trusts can be highly erotic and with ease bring them multiple orgasms when having sex with her partner.
Since there is a huge majority who likes that kink its always a good idea to add this into a game. Even in Porn the demand for incest porn is at a all time high and still rising. Even in literature thanks to GoT the demand for incest erotic novels is at an all time high. Its like people have opend a door that is socialy still a taboo but because it still is a taboo topic the people can't get enough of it. Like a drug for the mind.
NTR = watching someone you like/love getting fucked by someone else. Only cucks and people who like to being dominated get sexual pleasure out of this. That doesnt mean that people who like that kink would watch their wife or girlfriend/boyfriend/Husband fucking someone else in real life. Some do but the majority would not even consider it. Its like you watch someone cheat on you but you are ok with it.
While a minority of people who have that kink want to outlive it in reality as well, the majority does not (like with incest) and so its always a bad idea to add unavoidable NTR in any game but always a wise decision to make it optional.
So NTR = a minority kink and could ruin a good game simply because the majority of people are not into that kind of stuff.
This has to do with character consistency as well, why would you go to a lot of trouble wowing a woman that takes three years and 100's of dates to get interested in you and fucks everyone else in three minutes as a player. One of the few games with avoidable NTR that I have seen come close to character consistency is The Tyrant and that game is pretty romance light considering the high sex drive of the ladies on all paths. NTR with corruption incest can work though, since they are compatible, but with romance (incest) games I highly doubt it. What the romance players look for is just to different.
