There are three instances when you are unable to zoom with your feet to get closer to a wildlife subject. One is when there are physical obstacles in your way. Another is when approaching closer frightens away your subject. Another is simply there is not time to move closer.
This Barred Owl posed for me for a long time, but I could not get any closer than the edge of the deep ditch where I was standing.
I gave up on photo contests many years ago. The final image is my objective, and how I get to that point is not going to be dictated by some contest rules.
On top of that, many photo contests are for the benefit of those sponsoring them. Instead of having to pay photographers for the right to use their images, they charge them a fee for entering the contest and giving up their copyrights to the images. Instead of paying out fees to use your images, they take in thousands of dollars from entry fees from thousands of photographers.