Mimesis, for our purposes, means that art can adequately capture human experience and create a simulation in the readers mind when encountered.* This allows art to make assertions about human experience, assertions which can then be used to facilitate human understanding of life and govern action.
So, if we assume a piece of art to be mimetic, we can make arguments about what it means based on what it is communicating to a reader or viewer. Based on our operative definition, art can take abstract topics and either assert moral imperatives or explanations of how life operates as it is lived.
*When we discuss mimesis, it is not in contrast to diegesis.
The Bottom Line:
When teachers are asking for significance, sophistication, or meaning, they are really asking for what a piece of art is saying about a particular topic. Take for example the topic of Love. A piece of literature could assert the imperative of "Love your neighbor" or it could assert the explanation of "Love conquers all." The teacher wants a claim about the real world, but wants you to defend this claim using the components of the literature as evidence. Real life anecdotes can be used as clarifying examples to ground textual evidence, but shouldn't be the primary proof of the claim.
Starting out with Aesop's fables allows students to quickly read, analyze, and interpret the assertion. I use this to drive home the idea of mimesis with 9th graders.
The above document can be modified for any piece of fiction. The point is to show students that fictional acts can have real world equivalents.