People call the mc dumb, and alright, it might be stressful watch her do some things, but if you think from the psychological side it is understandable.
She lived all her life encaged in a “bird cage” and was abused by her fake father, all the while he said it was the better for her. It was quite clear that her mind wouldn't develop much more than the seven years she lived outside the count mansion.
And even if you say that the duke is useless for letting the count get her so easily, even if he wanted he's not the strongest in the noble hierarchy, so there should be some limitations to how much he can move to save her. Even so, the manhwa doesn't seen to be considering those so... they're mostly disposable arguments.
The only thing that bothers me is how fast people warmed up to her, especially the duke who seemed to be so wary of her before, although is not completely false that they would surely feel more attached to each other after the almost kidnapping she suffered inside the dukedom.
All in all, it's not a bad manhwa, there could be some little repairs, but surely it isn't a waste of your time to read. Pretty fun and with an adorable art.