In Korea, when people think of Rock, they think of Kim Kyungho or Yun Dohyun with long hair and in leather pants. If not but like idols, people are skeptical. Actually foreign rock bands like Coldplay have short hair, play ballads on the piano are highly recognized too. When CNBLUE debuted, they might have sought compromise. Now they write their own music and play live, a real rock band.
The above based on brief Chinese translation by 栖点 @ weibo, who also shared the video.