¿Cuáles son mis fallas? ¿por qué no fue aceptada mi fotografía?

Remember to always check your photos at 100% - 200% magnification to check for flaws.  It would have become even more apparent to you to see that this photo would have never been accepted.  As the other commenters said, it is severely overexposed and overprocessed to the point where the image is severely pixelated, has chromatic aberration and those odd horizontal lines in the blown out areas.

It would be worthwhile to review the requirements for submission.

• https://helpx.adobe.com/stock/contributor/help/photography-illustrations.html
• https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html

Better luck on your next submissions.

@koliber 1 is right. The photo is overexposed and the highlights have no details.

As an outdoor photographer, let me give you a suggestion, do not photograph animals from behind and try to get down level.