I have yet to see a successful live adaptation of a Korean webtoon series.
Some people might think that dramas that are based on webtoons, such as True Beauty, My ID Name is Gangnam Beauty, and Nevertheless, were very successful thanks to the cast and their acting skills. I hate to burst their bubbles, but they are absolutely wrong.
The buzz was generated by the cast themselves, and the fact that these webtoons have charms that cannot be translated accurately into television makes it resolute that webtoons should stay as it is.
Some webtoons rose into popularity because they offered certain elements that dramas and movies fail to incorporate in their plots, such as 19+ themes, their audacity to tackle relevant issues, and the freshness of it all. Webtoons are appealing because it allowed us to imagine the scenes ourselves, imagine the characters as ourselves, and imagine the plot happening to us. This is the element of webtoons that dramas and other live adaptations have failed to incorporate.
Some webtoons have mature themes, which made it successful to its readers. Deny it all you want, but sex sells. When the producers saw that these webtoons are highly popular among its readers, they fail to realize the reason why it was popular. It was popular because it has graphic scenes which appealed to the younger readers, and surprised the older readers. Thus, when they got the nod from the television stations to broadcast it, they cut the juicy scenes and replaced them with scenes that made the story totally disjointed and unrelated to the plot at all.
The writers and producers of these dramas had to follow the broadcasting guidelines when producing these dramas, and thus missed the chunk why it got all the readers excited in the first place. Also, some dramas were based on ongoing webtoons, such as True Beauty, and they totally changed the outcome of the plot just to suit the bill of their casting. Seojun was supposed to date Jukyung but in the drama, she ended with Suho. This caused a lot of complaints and commotion to the fans, who expected a faithful transition from webtoon to television drama and thus were left feeling betrayed.
Final note: let webtoons be webtoons, and let dramas have their own world. Drama writers should make it a habit to stay away from webtoons before killing the entire potential of the webtoon itself.