Hm you might be right there. I definitely recall her being incredibly dumb fairly early on though. Like, the kind of dumb that doesn't even know what sex or even arousal is.
She has always been offerd as a naive, inexperienced and purposefully sheltered girl/young woman - due to her mother's manipulative upbringing and strict desire for her to be married off to someone's family that could make the mother wealthy in the bargain. Look at the contrast with her best friend Elena, who had no such boundaries on her upbringing.
That set her up for falling slowly for her father, enhanced by his own unexpected desires and manipulations, among other things (such as influences by Elena or another incestuous couple, even on the D-only route).
I recently read about a Chinese couple in their twenties who were unable to conceive, despite many months of attempts. Eventually, a physician guessed the proper question to ask and then solved their problem - they gained a successful pregnancy not long after. Turns out they were having anal sex all along - they had no formal sexual education up to that point.
If you can't understand a story from another perspective, that's sometimes the story's fault and other times it might be yours.