According to answers in this post, a jet engine can suck a human into its engines, even on idle power. Aircraft use their engines post landing taxi and into their parking space, and I notice people directing the plane to and from the parking space while engines are on. Do they not risk getting ingested into the plane's engines?
A marshal should always ensure that he is in the line-of-sight of the pilot, failing to do so will effectively mean that the pilot is losing its extra sets of eyes. It is unable to see the hand gestures of the marshal guiding him into a parking spot.
To be visible for a modern jet liner pilot, you have to be meters in front of the nose of the aircraft. In the picture below, you have to be roughly on the right side of the orange line to be visible to the pilot. Modern airports use a digital marshal on a screen mounted to the terminal building.
Incidents of people getting sucked into the engine mostly happen due to miscommunication. Someone already walking up to the rear wheels with the blocks while the pilot spins up the engines to move the plane a little bit forward.
For a airliner there is no way to stay in sight of the pilot to guide them and be close enough to the engine to get sucked in. After the aircraft is parked the marshaller knows the danger zone for the engines and knows to stay away from them. In a lot of modern airports the marshaling is done by automatic systems and no external human is required to line the plane up.
There is a much bigger risk to the marchallers for the small GA propellor planes. There the spinning fan of death is right at chest height and if the pilot mishandles the controls could jerk the aircraft forward into the poor marshaller who only wanted to have all the planes on the apron in a neat row.