I just don't get the logic of being an "alpha chad" and giving your woman to another man. To me, that's the least "alpha" thing you can do. I don't like MMF threesomes but i can at least understand that kind of sharing, the MC is still involved. But playing as the guy that jerks off while another man has his way with his gf/wife? That's just pathetic. Why would i want to play as him? I'd rather play as the bull.
Now, since you want to talk about story and character development, i will just post a snippet from a review i saw on an NTR game to show you why i think 99% of NTR games belong in the bin.
This kind of thing is standard in NTR games. The women have no willpower and become cumdumps for the antagonist, the MC is a pathetic, braindead loser that couldn't do anything to stop it even if he tried. Is this what you call good storytelling and character development? lol.
As for harem, they usually aren't about cheating on your LI. Many of them have "helper" characters that are either ok with the MC seeing other women or encourage it. For example, Sandra from MNF, Glasha from Detective Necro, Carol from Now & Then. In a way, it's a role reversal from those sharing games you enjoy. Is it silly and unrealistic? Absolutely yes but i'd take that any day over playing as a cuck. Most of my favourite games are, in fact, not harem but rather games where you have to choose because the relationships feel more meaningful to me that way.