You are making a porn game. You cannot cater to all. What about gay people? Lesbians? Transformation? Fetish-lovers (including ntr)?
Just make a good game is my advice. And if you have content that is viewed controversial, it should not come as a surprise to players.
There do be popular ntr games out there. Having ntr is not the problem. But if you just add some random topics, like ntr, dickgirls, gay stuff, rape, incest, furry, pregnancy etc. , well everyone has their triggers that makes them avoid games. And yes, lack of certain fetishes is also a trigger.
ntr has the special problem of being ill defined. It would be being cheated on and being humiliated by your girl. She would not even have to cheat with another man. Without cheating or humiliation it is not ntr. But ntr haters will call threesomes, groupsex, open relationship, whoring, voyerism ntr, just because there is dick to be seen that ain't the mc's.