Well, I don't mind a build up as long as it's satisfying. With a Harem I think it's pretty simple, make sure the girls become committed to the MC, preferably no more unavoidable cuck scenes, and some payback for any betrayals and people that wronged us. I'm not asking for the Li's to immediately jump the MC's bones just for the harem choices to actually feel like they're affecting the story.
For the people that like NTR, Cucking, and sharing I hope they get what they want. But if the harem route has a bunch of unavoidable sex scenes and not enough scenes with just the MC and the LI's then you'll just be disappointing one group. And I'd like Katrin to regret going through with the threesome without a fight, feels like our words mean nothing to her. I don't wanna control her but our words affecting her decisions would be good. Until we get some payback for that on Brian AND Katrin I don't know if I personally would be able to deal with her without being frustrated with her. I was fine with the falshback sex scene cause it was before the game's current timeline, even when she came back late night to her husband cause we didn't know about it and didn't have time to do anything but with the threesome scene we knew about it and could have influenced her choice.
I'd also like it if the MC's thoughts reflected our choices more. Even while avoiding the cuck choices it still felt like you were trying to force us down the route of wanting to get cucked. I wanna see the MC frustrated about the Li's fucking those other bastards. Like if the MC felt frustrated or mad at himself for not being able to stop Katrin or mad at whoever's fucking her I wouldn't have been as upset as I was with the unavoidable threesome.
Frankly just don't neglect content on the Harem route. Neglecting any route in favor of another route whether it's NTR, Cucking, Sharing, or Harem is probably the worst thing a dev can do in my opinion.
