The top reason why Supernatural became worse after season 5 in particular is because of certain staff changes that occurred at this point. From the start, Eric Kripke was the creator and main showrunner of Supernatural. He gave the show its dark, grungy ambiance and horror-centric themes.

One of the absolute worst episodes of Supernatural across all the seasons is the season nine episode, "Bloodlines." The episode was panned by critics and audiences alike when it premiered, and not an episode fans rewatch when binging Supernatural again.