The product of an individual's mind is not the same as the mathematical average of the products of everyone's minds. The latter is obviously going to lack any of the uniqueness of the former.

Current models absolutely suck at writing fictional characters, by the way. And they're getting worse. Seriously, try it yourself: have Claude write a story with a decent amount of dialogue involving character A, then have it write another story involving a completely different character B, then compare the dialogue between the two. You'll quickly notice the same blatantly unnatural speech patterns in both.