The necromorphs were an incomplete species. No, it would be better to call them a defense mechanism that can easily be shut down when their purpose is accomplished.
But it didn't mean they were weak, they were only limited by the signals, as long as they received it, they would never stop moving. It was one of the reasons why the necromorphs always spread like roots and if someone were to destroy the head of the root, all the necromorphs would stop moving.
It was a limit intrinsically designed into them.
Though, Sitara who was the current base for the controller of these undead beasts found a loophole in this.
She created a subroutine that can act as its own signal tower and imprinted it inside a few chosen individuals who were later called the Priest of Necromorphs. With Kismet being the sole player to obtain this special class.
It was why she can move the necromorphs, even though they were so far out of the signal range of their activity.