Yes big snakes can eat big animals but apparently even the Anaconda cannot eat a full grown adult human . There have been deaths of people drowning after being pulled into the water . No snakes jaws will go over the shoulders of an adult , they can kill a grown human by asphyxiation but not swallow .
A consricting snake doesn't just suffocate you.. It is also breaking bones and making you nice and squishy.
Shoulders are not a problem.