If you want a simple example, you could just have an episode without featuring any of the Main 6/7, or maybe just have a cameo of Twilight at first to smooth the narrative, and then follow the rest of the episode with just the princesses, who end up arguing like it happened in the episode, but then they agree on the mutual idea of switching their duties for the sake of proving their points. You then get the same shenanigans without having to waste time on Starlight, and all the dream-land stuff happening at the end can be easily brought from just having Celestia watch over Luna’s nightmares. Similar conclusion in the end, and we get even more time for the actual princesses to flesh them out and avoid things looking forced. There, I just described to you how this episode could have worked just fine, perhaps even better, without Starlight Glimmer having to be a part of it.