Castaway Diva has 'castaway' only in the name. Most of the characters she encounters don't care how she survived on that island all alone. The castaway situation was just reduced into some throw away lines between the characters. Her being a castaway provides nothing to the story after 2 episodes. It becomes completely irrelevant. There is no sign of psychological issues from spending all those years alone in that island. There is no struggle for her to get accustomed to the society. That also was fixed easily through some throw away lines. There is no struggle for her to overcome inorder for her to become a singer. Everyone just accepts that her easily without any conflict no questions asked. If you know anything about korean entertainment industry and media, that's not how that work.

The story was more focused on the ML's story rather than the title character. The main plotline is sidelined by the ML's traumatic home life which was much more interesting than whatever going on with Mok Ha (FL) and Ran Joo (SFL) for sure. But thats where the title of this drama comes in as extremely misleading. Everything here felt so rushed and cut short.
And for there are some extremely good actors playing there characters really fantastic. Most actors did a wonderful job, especially the actors who played young Kiho (ML) and Mok Ha.
The OSTs were really remarkable.
Cinematography and direction was superb particularly the visuals.
And this drama had one of the best pilot episode I have ever seen in tv.
All things considered, the only things that I feel is indifference rather than disappointment with this one.
I'll give it 8.5 only because I could finish it and I am often generous with ratings.

P.S :- Ran Joo is not a good or reliable person. The CEO guy and Eun Morae was 100% right about her and had very good reason to abandon her. (my unpopular opinion)