I've played a lot of these games in the last few years, and I'm surprised people are so harsh on the MC in this one, especially in comparison to other games. I mean, I suppose you could argue that the game was written intentionally to put him in these positions, but just looking at the story I see him getting along quite well with the youngest daughter and hitting things off pretty well.
With the middle sister, she is emphatically against him. I'm pretty sure she even slaps him at one point, which he deserved, for spanking or kissing her on the ass without warning, which isn't exactly "spineless." So, what should he do about it? Hit her back and get into a fistfight? Instead, he kills her with kindness, which drives her absolutely crazy, and ultimately wins her over. She has him act as a slave for a day (in exchange for some favor I think, I forget why, but there was a reason), and the end result is he gets to have a sexual encounter with her. He doesn't complain. He then shoves his face in her vagina while she's just trying to do sit-ups. Again, not the act of a spineless man. Would it have been better if he went all-in and forced his way into a relationship with her from the beginning when she clearly said she didn't like him? That's not "having a spine," that's being a predator. There are plenty of those MC's in other games. I'm happy to play a character that's not completely an irredeemable asshole this time around. As it is, he's pushing what's reasonable.
What about Quinn? He already wantonly stares at her tits and gets away with it, and she just laughs it off and enjoys it. She flirts with him, but he can't tell if she's serious or just messing with him. He's afraid of her, and isn't sure what she would do if he flirts back. She could easily over power him physically, and he's not sure what she's capable of morally. So what is he supposed to do to "turn the tables?" I suppose he could blackmail her or drug her and--oh wait, that's exactly what everyone is complaining about her doing! And again I say, if you've been paying attention to her character this whole time, wrestling him into submission, coercing him with gunplay and handcuffs, how are you so surprised by this?
He tells his mother he wants more from her, and respects it when she says she's not ready for that.
That is what's supposed to happen with normal rational people.
I kind of feel like a lot of people are describing "respecting other peoples' wishes and personal space" and "having rational fears of dangerous people" as being "spineless." Should he have been buying lingerie and flowers and professing his lust for his own family on a daily basis? He's already boning his entire family inside of a month of moving in with them. I think he's getting by just fine as it is.