No I totally agree, I remember downloading CmA since the premise looked promising and just reading over the walkthrough saw the grind involved and (no surprise its a sandbox) and basically said fuck that. I don't mind the occasional lez/bisexual group sex primarily if the MC is involved or allows it, but never behind his back and yes, it is a tired trope that every girl magically seems to be bisexual or bi-curious.
That said, something about Haley just bugged me from the beginning when she was first introduced. Maybe its the inherent problem I have when my MC is automatically in a relationship where I did not have a choice in the matter, sometimes (if its a wife I can kind of overlook it) its handled better than others but I never quite wanted her around once Nikki was up for resuming a sexual relationship with the MC.
If I want romance, I'd rather just go after both Mom and Aunt Nikki, which as it happens is my canon path. Just to be a completionist, I did do a harem path with Haley.... it was ok, but she's just not my preferred girlfriend, it didn't bug me how thirsty she was for Nikki initially, it was comical and a little hot at first.... right up until we caught her with her with her face buried between Nikki's thighs. I wish we could have had the choice at that point to yell at them both and angrily turn down the proposed threesome. The LAST thing I wanted to do was reward my girlfriend for cheating on me (yes I'm a hypocrite, but I don't share my L.I. unless its my idea) regardless if its with a guy or a girl. I probably would have not been so angry or upset if Haley came to me first and talked about her feelings for Nikki and proposed a threesome or even asked Nikki about a potential 'experimental' threesome to avoid any cheating or jealousy while she got to scratch her bi-curious itch. I know this just fantasy but again, playing as the MC, if I saw my girlfriend actively cheating on me, you can believe not only is a threesome NOT happening, but we're done... I'm breaking up with her on the spot and she can go home immediately.
As far as Nikki goes, I'd tell her how disappointed I was in her decision making... if she wants to fool around with a girl, that's fine as we're not dating, but she should have thought about that with her nephew's girlfriend, unless she was either just assuming I'd be ok with it, or if she was looking to break us up. I'd actually respect her more if it was the latter than the former as it would at least tell me how she really felt about me.