According to someone on Novelupdates who looked up the webnovel reviews, the story seems to be very well-received by Korean readers.
https://forum.novelupdates.com/threads/the-crown-princess-audition.109363/page-2
Turns out the main focus is more on political intrigue/survival and has little romance.
Prince is going to become a human sacrifice once he turns 20. Magic weakens once a while, and the nobles are the only one who can use magic. The nobles will sacrifice a chosen one during this period (ex. the prince) and split up the sacrifice's power among themselves.
the plot is a bit dumb.. why go along with something you know that there's something wrong??? its like am reading mystic messenger..... dumb protagonist thats been keeping swept away with the flow
it's obvious that the one who instigated the search was the one that stole it (probably anyway). anyways it's nice to see that the two (sisters?) have gotten closer.