SPOILER WARNING
Cuckqueanry (which is the term you mean btw) is INFIDELITY within a COMMITTED relationship, and requires the woman to be a passive party in the sexual dynamic. Cheating requires a lack of consent from at least one person in a relationship. Consensual discussions of kinks regarding multiple partners and talking about THEORETICAL multi-partner relationships and sex is NOT cheating, especially since the MC is actively participative in those discussions. She is not yet officially with any of the guys while this is happening-they're still at the flirting/casual sexting stage for a majority of the game.
If threesomes and polyamory are not your thing, if you don't relate to the MC, who *is* mostly kink-positive, then that's valid, but at least be accurate about your complaint. And you chose the obvious "threesome" answer in Leland's route yourself, then are gonna complain about his answer? Touch fire, get burned. So Sasha is into threesomes, and so is Leland. Some people are into those kinks; it doesn't change the fact that they're into the MC too, which is what the game advertises. If that's not for you, then there are other LIs in this game. Not every LI is going to be every player's thing.
The game is kink-heavy and has a lot of discussions on unconventional sexual preferences and relationships (bondage, pet play, gender-bending, dominance and submission, and yes, multi-partner fantasies). That's not everyone's cup of tea and that's fine, feel free not to like this game. There are other less kink-oriented games out there with fully-heterosexual LIs if that's your preference.
But polyamory/orgies (that are only in theoretical discussions and kinky/dirty talk btw and not actual in-game events) are not, by definition, cuckoldry/cuckqueanry and infidelity, and stating that this game portrays them when it does not *is* misleading.