Well, it's the first and last sageuk I'll watch. It is a classic, well-made, well-performed melodrama with well-sketched out and memorable characters, beautiful BGMs and cinematography, and even though it's tragic throughout, I did not mind the tears.
The attention to detail and tragic-comic aspects in showing the lives of court ladies and sisterhood, court politics, intrigues and controversies, the grandfather/King's dementia, the longing of the ML (CP, later King) for this 'lowly' woman (who would've been otherwise forgettable in a sea of 700 available women and girls, and noble consorts), and the FL's resolution to 'stay in her place' and have a bit of freedom (especially since she could never be equal to the CP/King), all made sense.
Considering that this was a fictionalized version of a true story where the King asked a court lady 3 times in 14 years to be a consort and she kept rejecting him (without repercussions), but became the concubine after he chose her officially by issuing an order/command when both were in late 20s. He lived with her as the only woman in his life for 6 years before she died. Who knows whether this is actually true or merely how the King wanted his 'favorite' concubine to be remembered, but since this kind of longing was unheard of for rulers, is what makes this retelling - as embellished and mysterious as it may be - worthwhile.
It made for a great drama, tears and joy and fear. Everyone and everything (including that CGI tiger) made sense.
But the drama should've shown ML/King interacting with his next-born heir (with the 'selected' concubine who came after FL's death). They showed everyone except his next 'family' who outlived him.
The FL's life as his favorite concubine was shown to be a bit miserable like 'Raise the Red Lantern' though I wished she'd transcribed or done something meaningful with her time.
The King's dream / hallucination on his death bed of reuniting with the FL and her 'openly loving' him by showering him with hugs and kisses which she never initiated even as his consort was IMO just his wishful thinking and longing to be openly loved by her like he did, because he always remained unsure of her true feelings - it was the kind of hallucination people get right before dying / in coma. It certainly wasn't the afterlife because FL would've probably chosen everyone else and her freedom over being with him forever in her afterlife. Just like it was mostly a one-sided love, it was a one-sided dream / hallucination from his death bed/ right before death.
Most of the drama was morbid, dire and hopeless with comic warmth brooding over it. But whatever it was, as painful and wistful as it was, it was great to watch it.