2 Years of Service
NTR and sharing are two different tags, though people who are into harem games often don't like either. The problem is you're applying real-world standards to porn, harems are a convenient way to have a bunch of love interests that fit different peoples' tastes all act as devoted partners to the main character, which is the fantasy. I like it when the LIs love each other too because I'm into lesbian porn, but a lot of my harem compatriots don't because they're really into the committed partnership part (or they just don't like lesbian porn).
Also neither of those tags are anywhere near the most misogynistic or morally repugnant options. Like all the games where the MC is a reluctant slaveowner by circumstance and all his slaves are in love with him (e.g. From the Eclipse) so the player doesn't have to be the bad guy but can still do the slavegirl fantasy thing. On the other hand games like Free Cities own the MC being irredeemably evil, and you basically abuse the slave girls into loving you.
In my opinion, NTR, sharing and cheating are three different things. Traditional NTR, like in japanese games, is a lot more than just cheating or sharing. The game make you invest a lot emotionally into a character then make you watch this character being fuck by some other people. It's a kind of emotion manipulative game for people who like the horns they have on the head and for those who like to be blueballed. NTR provoke strange reactions in me, on one hand, it may excite me a lot if done right, on second hand, it make me feel culpability (which is strange as i often play game with darker theme and don't really feel that) and on the third hand i just don't really like them anyway (because i'm a woman, story is important for me and NTR is often use as an easy plot by lazy dev with no creativity).
Even in real life, it's complex. There is an increasing number of people who build relationship outside of mandatory cishet monogamy. It can be without every people consenting (cheating) or with every people consenting (swinging, open relationship or polyamory).