Demystifying my technical issues

I am a new contributor and would really like to undertand the specific reasons for the rejections of the vast majority of my photos. I’m mostly a wildlife photographer, but do a variety of photos, with landscapes and some people. I’d say at least 60-70% of my photos have been rejected, which is quite a blow to the ego! The point of confusion is the (to me)  is the seeming lack of difference between ones that were accepted and ones that are rejected.

I was going to upload 4 photos - 2 rejections and 2 acceptances - but I can only upload three. So I will use these for illustration. The top photo of the tanager was accepted, but the wombat and toucan barbet were rejected. I took them with the same camera, did similar amount of processing, and had similar camera settings. 

Granted these are all animals, but to me they at least reflect the (to me) lack of contrast in quality).

I am very tempted to stop uploading to Adobe altogether, but if I understood what the issues are with my photos, perhaps I’d try one more time.

Thank you so much for any insight. Best wishes.