Why was my photo rejected due to quality?

Here is an idea incorperating what all have told you.

I wouldn't say this photo is exactly good, but it doesn't look terrible. There is no overexposure, underexposure, there is not much noise. The photo does not look crowded. Please tell me what is the problem and what is wrong?

By @fast_2624

Your image is flat.

There is no depth to your photo. It lacks contrast.

Also, remove the blurred-out images in the foreground, left and right bottom.

There are a few things you can do to improve the photo.

underexposed. the foreground needs removed and the flying bird in the middle needs removed.

It is in fact underexposed and those two objects at the bottom should be removed.

Focus is very soft, shadows are underexposed, and the white balance is too blue.