I mostly loved this show. It touches on a specific time in Korean history, starting in relative chaos and through considerable struggle and pain, settling into a time of peace, and one hopes relative prosperity under a king who it seems was certainly "enlightened". I don't know this history really, but many Korean people probably have strong opinions on the drama. My own opinions are mostly constrained to the frame of the drama itself, with some tiny reflection from a little bit of reading.
It is beautifully written (mostly) and extremely well made, well paced and of course the acting is universally wonderful. The show is heavily focussed on the relationship between the two leads, and this was well delineated ... most of the time.
The FL was believably feisty - or was it unrealistic for a girl in her position, whatever her gifts? Never mind - I loved that about her - she had guts, but was never rash - though accused of this often. The ML was also excellent, but I felt that mostly this drama was owned by the FL. Both actors were fittingly beautiful in their roles.
In regards to other relationships in the drama - all were wonderful, most were tragic, and some were a bit toxic. But mostly this film centred on the main relationship, and the couple's satellites - thankfully, the sometimes excessive court intrigues were kept relatively under control. I lose interest in those very quickly.
Well, all of the above was great, so ... I felt after the death of Uibin this drama lost any impetus and all dramatic tension - it was an essay in restrained grief, which was set against a lot of quite decent emoting riding on a pretty soupy musical track.
On that note (pun intended), while there was little really wrong with the soundtrack in itself, it was set at a level which was far too intrusive for me. Considering that at this time most of life would be lived among sounds of nature, or of labour, or of silence if you were very privileged, I find these grand orchestral soundtracks overwhelming and sometimes completely inappropriate. Most of the action was backed with such intrusive noise and that spoiled the drama for me - at times it was just awful. It was much more watchable when there was silence.
The last few episodes clearly showed how Deok Im's life was almost totally stultified by being obliged to "serve" the king, but ironically also truncated Uibin's life as a concubine (never mentioning the child who survived her to be crowned). After her accelerated demise, King San's remaining years were sketched in with a very light hand indeed - and a lot of soupy music. Little was said of his actual achievements other than that he was the first benevolent monarch of Joseon. Unless I'm missing a LOT - and if I am it's because this exposition failed to keep my attention!
These last episodes were overly sentimental and a great disappointment to me. Really the series should have ended with the death of Uibin and some exposition of the King's somewhat distorted grief. Surely her funeral would have made a sensible ending.
In many ways, this was an excellent series with many fantastic characteristics, marred by an intrusive soundtrack and (perhaps) a somewhat indulgent ending.
All of the above said, I would still recommend it to others, but, yes, might attach a hazard warning ....