YES, this is what the story is missing! Mystery and suspense! something to keep the story interesting (๑•ㅂ•)و✧
I can really agree with you in the fact that we know many things that the villain doesn't know, therefore due to this misunderstanding we view her as stupid, like for example if I was suddenly put into this story without the knowledge I'd think its absurd of them to poison him. Only to then realise that it's for his own good. However she has the knowledge so she should have even the slightest bit of awareness behind the intentions behind poisoning him, before determining that its evil to do so, and that she has a better way to educate him. But I guess with limited information, she won't really know...ヾ(❀╹◡╹)ﾉ~
I don't mind the mc's character. I don't think she's dumb, but she is more of a feeler than a thinker (personality trait). I don't mind her having strong feelings and morals. But, I think this would be a very interesting novel if some things were skewed in perspective. For instance, less knowledge about the duke or kid's intentions. we're too sympathetic towards them, to the point where we think MC is dumb because she can't see what we obviously know from other scenes. I would have liked being left in the dark because that adds suspense, mystery and puts the audience in the same situation as MC of feeling vulnerable and wary. It would have been a fun ride if we seriously got duped by the kid's act, then it was revealed like 50 chapters later how cruel he is, instead of in 2 chap. I don't have an issue with the plot or characters, but I think some misdirection would have made flat characters seem so much more complex. If it changed the narrative slightly I could totally see this as more of a suspense, mild horror, romance, historical webtoon.