Alone the concept of realism needs a whole lesson: we want a good mockup and good mixing. The realism of the copy is relative to the reference. If the reference is you as a listener in the hall, this is one thing.If your reference is a mixed soundtrack in a genre that sounds anyway more artificial , this is another “realism”. In this case we speak more about the mockup being authentic and good than being real. Important is the clarity and vision that you have about the reference, and how your taste judge between two or more references.