Short answer? No.
Long answer?
It's optional, yes. I'm fixing some of the tags right. And I'll add planned tags. I'm still getting used to the tools in the forum. I'll fix it ASAP.
Not really. It's optional.
I don't want to give too much spoilers.
I really wouldn't say MC is a cuck. He's not getting off on that and he doesn't have any relationship with any of the girls whatsoever. I mean, if Lex Luthor seduces Louis Lane and fucks her. Who's the cuck, Lex or Clark?
As for the RPG mechanics. For now, girls only have Inhibition and Corruption for stats. Improving your stats only makes the game easier. (Higher charisma equals higher chance of seducing any of the girls, higher corruption increasing during scenes. Higher corruption equals lewder scenes. Lower inhibition equals more public scenes, etc.). It's not necessary. It just adds depth, and allows me to explore and experimentate a few ways to add more scenes. Though this feature is not yet fully implemented. And I'm still thinking about a good way to add this to the game without making it too grindy or boring.
Well, there's no way to please everybody. While I'm still an amateur, I do like darker art ambientation. But I do realize there's plenty to improve.