Sorry for the delayed response (does spending the day at the dentist office count?) :-)
First reaction when this image loaded was the perceived tilt. Technically I don't believe it is; it's that angled tree line and the use of what I'm assuming is a wide-angle lens (trees converging in the center). The stars visible in the area below the opening, beyond the foreground trees, look sharp - the ones in the open area are showing some movement. Hard not to I know ... just saying. I'd have hovered between a 5 or 6 on this and probably hit the 5 and moved on.
Can't add anything that others haven't said. I'm guilty of giving you a 5 for this. I like the image, it's a nice evening shot, but as Lydia said, there's no definable subject and the trees do give the appearance of the horizon not being completely level. To me there was nothing really wrong with the image, but it just didn't grab me.
Not sure whether the horizon in not level... or the tree line is making it appear that way... but I think that's part of the reason for your placement.
Also, something that's clearly the subject would make this better, IMO. My eyes go round and round... searching for a place to land.