It's a nice picture. But I do not think the camera was level (look at the horizon). This is recognised as a composition error.
The reason for the rejection is noise:
ISO1000 generates a lot of noise, and you had options as the exposure time is 1/1600s. I would also have closed the aperture a bit. The asset is also missing some contrast.
In addition to the noise reported by @Abambo, there's a spot in the sky, probably a bird, but looks like a sensor spot. I would edit it out. The foliage in the left side of the image is dark and underexposed.
Not only the noise and the tilted horizon are a problem. The highlights in the sky are overexposed and the shadows are under exposed.