I feel like Apothecary Diaries is exemplary proof that writing quality depends not on which tropes are used, but on how they're used. The yeast of that story ferments on one of the most maligned and frustrating tropes in existence, and yet it's executed so well that the bread is delicious with a nice firm crust.
MaoMao and Jinshi are both intelligent in a lot of ways, including deductive reasoning. So one might expect their repeated misunderstandings or continued blindness toward certain revelations to feel contrived. But they never do, in part because of how brilliantly their characterization was established.
From the first installment, Maomao ponders how "knowing too much" could get her into trouble.
At first her main concern is her own literacy. The ability to read is not a skill most young women of her station possess, and would doubtlessly draw attention. Attention threatens her ability to lay low and wait out her service contract. So she keeps this skill hidden.
And indeed, her concerns are validated by the narrative, because she catches the attention of Jinshi and Gyokuyou—two of the highest authority figures of the rear palace—immediately upon employing her literacy in her effort to warn the concubines of the poisonous effects of the makeup.
This instantly alters the course of her life, a consequence that at first seems positive; after all, personal attendant to a concubine is certainly several steps above the average palace launderess. But these elevated steps bring more attention onto her, and it isn't long at all before the emperor himself is ordering her to perform medical miracles.
Knowledge is power. And as Maomao explains to Jinshi: it's not always about what someone will do with power; it's about what they can do.
So Maomao uses the powerlessness of her station as a shield, and hides behind it by pretending not to know things.
And the way she does this is interesting, in part because she is so good at deduction. Often it comes down to her simply choosing not to pursue a line of thinking, forcefully redirecting her attention elsewhere the moment she realizes that certain lines may connect to form a bigger picture than someone of her station should see.
Maomao is an apothecary. Effectively, throughout the story, she's an herbalist, pharmacist, chemist, physician, dietician, and forensic detective.
At the same time, her primary survival mechanism is avoidance. And this is established very early in her characterization, even before her actual titular passion.
When Maomao, solver of mysterious deaths, worker of medical miracles, foiler of assassination plots, repeatedly fails to connect the increasingly-obvious dots pointing to Jinshi's true identity, it doesn't feel contrived at all; because by the time those dots begin to come to light, the story has already established that it's firmly in-character for Maomao to simply refuse to pick up the pencil if she already knows what picture those dots will form. As long as she doesn't draw those connections herself, she can remain safe in denial.
And that's how Apothecary Diaries turned one of my least-favorite tropes into one of the most compelling parts of its story.