This drama had so much potential given that this is Kim Min Gue and Ko Bo-Gyeol's first leading role and the two of them are known for their amazing acting chops.
The plot was very promising, The idea of a high priest that got his body switched to a K-Pop Idol was interesting and fun, and Kim Min Gue really delivered on his performance as Yeon Woo / Rembrary. But the story became stale quickly and it got to a point where it became too dark and unbearable to watch.
I understand that this is a fantasy drama however Idol storyline of the male lead becomes too unrealistic, In Korea, once an Idol becomes involved with a lot of controversies they will be viewed as problematic and it will basically lead them to stardoom. So with the main character suffering from controversies left and right it's impossible that he always manages to make a comeback every time. It's also annoying that the male lead had to suffer multiple times only to get what ??? get betrayed by his people ??? The story doesn't make sense.
I also had high hopes for the female lead as I have seen her performance in Hi Bye! Mama. She really had great potential but I don't know what happened to her in this drama ??? There were moments where the acting was so stale that it almost seem like she is an amateur actress. Did she get too pressured because this is her first lead role??? I mean what happened?

All in all, I would say that this is a case of a drama that has a good premise but weak execution.