This picture has so many clouds that I can't see the sky at all. I think that what makes a great sky picture is an abundance of clouds but also the separation of clouds and sky. There needs to be more land visible. It looks like you punch up the contrast yourself, I can tell by the photo without reading your comments. There is also grain visible, maybe that was your intent. It looks like the the far left hand corner there is some sunlight trying to peek through the clouds, I would have focused on that. As far as your title, There is dark, but not much light. Skylines are not easy pictures to take. It is alot of sit and wait for the right cloud formation and you also have to have a great landscape sometimes to go with it. I would say to keep trying! Look up and shoot until you get that perfect shot! Good luck in future challenges!! I hope this was helpful.
The trees seem to just be in the way at this angle. They need to be framing the photo better so as to draw attention to the subject--the sky. Wild sky.