I think what made up for the lacks and potholes in the emperor was the attention to the side factors, seemingly unimportant elements of each scenes. From the beautiful landscapes, the plant blossoms, the stunning sunsets, the demeanor of the locals going about their business in a very matter-of fact way, the customes🥰(although I felt they could've done better with the Kings' and Queen dowagers' official wardrobe) and the soundtracks were simply amazing.

*Okay I'm a huge saeguk fan,no no.... I'm an unrepentant hooogeee!! fan of Kdramas 😩😊
I'll recommend this drama for the love of Korean historicals.*

*The not so good*....... Ga Eun🤦🏽‍♀️, her appearance in the first episode promised alot more but about two episodes down the line,the character turned out a disappointment. As the student of medicine and a pupil of former Sungkyunkwan master,she deserved a better script than playing the trophy girl in distress. The script made it seem as though the crown Prince's character would've been utterly useless without him running over the place on her matter, with the initial plot, she ought to have been a sort of (bong Yun, roots of the throne) and not a Rapunzel waiting to be swooped, making ridiculous decisions without communication despite knowing the current challenges faced,(then there's the rushed affection between her and the CPrince, it sort of felt like the prince developed "intense love" for her mostly beacause of his role in her father's death) with the way the romance turned out, it was utterly ridiculous for her to run off as a court lady without discussions or proper planning which betrayed the "die for you" peak of their romance since at that rate she'd have known what'd crush the prince but noo....'ima jump into the war zone and hope for utopian salvation' especially when she (without backup)made those outrageous trip to the Kings' room to sniff around. Another betrayal of the supposed "hot romance" was Ga eun-ah becoming a clueless puppet when it came to her deceased father and his honor, she seemed to suggest for half of the entire drama that the Crown prince(as lord Cheon soo) be damned until she regained her father's honor.
And there's poor Hwa gun, exceptional second FL, brilliant, thoughtful and I incredibly loyal to the brutal end, after all those story saving sacrifices,she ended up sadly, it was agonizing to say the least though that sad fate is very much understandable because shits like that happen more often in life than desired.
In all, the actors did well, the potholes was in the script writing because So hyun and others would've done better but for characters scripts being poorly developed.

Nevertheless, I'll recommend this drama to absolutely anyone, especially those like myself who find pleasure in other aspects of Kdrama than the scripting.