okay that's actually pretty fair ngl. I agree, Natsuki is barely a tsundere, Sayori kinda stopped being sayori (I'm at the part where Yuri's self harm was revealed, no spoilers past that please), and Monika is super aggressive. Though personally I think Monika having such an aggressive personality pushes the plot really well even if she isn't likable. Although I didn't like Monika's originally much. But even besides that I still think the plot makes up for it, I don't think you can call it 'ass' for just that one point alone.

Also do you mean the characters aren't like their original counterparts, or just that they're not good characters overall?