Long range marksmanship is definitly an advantage but another real important part is skill at identifying the animals at a distance.
For me, locking onto the correct animal is more difficult than the shot.
I hunt alone and use 40X binocs (pretty standard). Often in the short time it takes to shift from my binocs to my scope, animals have shifted and I no longer have a posititve ID.
Other factors add to the difficulty - antelope shift around a lot, and the does sometimes have horns - sometimes bigger horns than you would think. Dust, heat waves and shimmers, shadows, and poor light conditions play a part. I've even made the mistake of shooting a smaller animal when a larger one was there to be had. I'm pretty confident in my shot out to about 400yds but I find that the longer the shot, the longer time it takes for the setup.
Having a spotter helps a lot. I am sure that good magnification on a scope helps a lot, but I don't have that.