Without a doubt one of the hardest parts on mule deer is getting drawn. I have hunted antelope spot and stalk, elk, pigs, etc. By in large mule deer tend to be the one animal that do not tolerate the draw very well.
Many things can go wrong. Many stalks end before they even get started, wind swirl, busting a doe out, running a coyote into the deer. I have had a golden eagle ruin a stalk once. This last weekend I had bucks at 53, 42, and 28 yards. All 3 opportunities were lost for various reasons. Trying to draw is one of them.
It is also a very interesting topic. This is a main reason why archery guys including the Colorado Bow Hunters Association are opposed to the use of crossbows during archery only seasons. It is a huge barrier to success, crossbows or draw lock mechanism tend to change the game significantly. Getting close to an animal is one thing with a bow, but getting to full draw and shooting is a whole another game.
For me I would say 30% of my stalks are blown before I ever get in range. 70% of my stalks allow me to get into range. However less than 10% allow me to get to full draw. And less than 3% allow me to shoot.... Those are just rough numbers.
I used to have a lot higher percent of stalks that would end before I was close, but I have gotten better at making sure the stalk has a chance, I have gotten better at moving and using cover. But the one area where it will always be hard is getting drawn while having the animal in position to shoot.