Possible Clues:

• Mechanical writing found to be lacking in diversity
• Like Spacey playing in pioneer parts too often?
• Model found to be lacking new parts
• Shy characters primarily engaged for similar roles
• Restrict player's scope in characters and acts, perhaps
• Given the same sort of parts
• Always given similar role
• Work in the pool shed's pigeonhole
• Pigeonholed, in moviedom
• Characters on pitch always playing similar roles