Man, it just occurred to me that it COULD have been Quinn's song. This episode could have been about that realization she has right then, that she doesn't want this, and instead of the camera and storyline suddenly ditching her to follow Rachel, she could have written a song and sung it and broken up with Finn. And then Rachel could have gotten her gold star and it would have meant something because I wouldn't be sick of her. And Quinn's song could have been something actually designed for her amazing but completely un-Rachel-like voice.

But only one woman is allowed to be a real person at a time on this show, so of course not. (Well, "real" meaning "incredibly sexist writing but is allowed up to three personality traits rather than the usual one, and her storyline is actually followed across multiple episodes usually.")