My first impression is that I like the backlit palm leaf.
Meeting the challenge - This is most likely where your score suffered the most. While shadows are an element here, I don't think they are a strong enough element. IMO the challenge requires that the shadow be a major element of the photo or at least makes the photo better because of its presence. I don't think that happens here.
The busy background isn't helping the aesthetics of your photo either.
The composition is good. I like that the subject is of center. The eye is drawn in then out from the palm. The exposure and the angle are good too.
I think if the shadow element was more prominent this photo would have scored much better.
I hope this helps. Feel free to contact me if you have any questions.
There isn't much focus on a shadow here. From a technical aspect, I think it would have been better if you had the plant up front. in the top left corner there is a green plant blocking part of it and at the bottom center there is dead area in font of it. Those are sort of distracting from the photo.