imo reviews and comments are too extreme - i agree it isn't the best saeguk out there. it has several flaws in the writing and the plot sort of fell off after ep 10-12. if you came in looking for a politically-driven drama, this was definitely not it since the beginning. if you read the synopsis of this drama and expect strong politics, that's on you tbh because it screams romance-centered. "political" is not even a tag here, so judging it for having weak politics is out of place, since it wasn't even part of the main plot. the plot is clearly about how the female twin survives as the CP and develops feelings for her royal teacher, and that's pretty much what delivered. now, again, i agree it wasn't the best after the leads got together and the second half was underwhelming and draggy, but most of the reviews are focusing on things unrelated to this particular drama, and bringing up plots from other saeguks. the fact that it's a saeguk doesn't mean it needs go be politics-centered.
that said, it would've been better off if it had 16 eps as the regular format so that some of the writing mistakes wouldn't be so noticeable or bothersome. i feel like the writer forgot about certain characters throughout the drama and remembered them only by the end (tho they did have a purpose), which shows kind of lazy writing. it feels like the writer ran out of inspiration in the second act and didn't know what else to throw to the plot, but kind of recovered by eps 19-20 and produced a nice 3rd act (for me). these two were the best of the second half and gave a nice closure to the drama. overall, i did enjoy it but i'm also a rowoon stan, so i'm aware that my judgement isn't completely unbiased, lol. tho i wouldn't really recommend it to someone who isn't into saeguks, and maybe only if they like a lot of romance and rowoon, lol.