The focus of the writers has been moved towards the use of metaphors in their writings.
 The focus of the writers has moved towards the use of metaphors in their writings.
There is indeed a difference.  is an agentless passive clause; agentless because it doesn’t say who or what it is that has caused the focus of the writers to move. Taken in isolation, it’s likely that someone reading that sentence would be left wondering about the identity of the entity or entities involved.
The active clause  on the other hand merely states the fact that the focus of the writers has moved. There’s no hint that some unspecified person or thing one has caused the focus to move, and the reader is likely to simply accept the fact and move on.
Both sentences are grammatically okay.