Okay, I am going to start by saying I got to know this show because of Taehyung. I didn't watch this show because of Taehyung, but it did come in my radar because of him.
The show, though only 20 hours long, feels like it got too much run time. The main female lead lacked personality or character strength. There were too many loose ends. For example: what happened to the princess? The ending was...balanced in a very rough and raw way. One got the throne, the other got the girl. However, other than that, loose ends upon loose ends were littered throughout the series. The rest of the Hwarang was wrapped up relatively...ok. Not too bad, but not excellent. The ending episodes are too rough.