I honestly don't know where to start. The (very slightly) above average rating is mostly due to the acting and general K-drama feel of the show. That being said...

1. None of the characters had any chemistry whatsoever. I didn't believe that Jungwoo had feelings for either of them but at least he and Taeyoung actually had kiss scenes (if you could even call them that, it was more like they were kissing a wall)
2. The storyline had potential, but was ruined by the omittance of major plot points
3. There was really no need for there to be a different conflict every episode. It was so hard to follow

Personally, this would have been better as a bromance/friendship drama. The 'romance' didn't necessarily take away from it, but it also didn't add anything. At least it did have a happy ending and, of course, stellar OSTs (thanks to Leo and Karam)