Summary

• Some long-running TV shows face a decline in quality as they continue due to overextension.
• Procedural shows can sustain quality due to real-life inspiration, while fictional dramas struggle.
• The departure of original characters led to Grey's Anatomy losing its charm over time.

Many popular long-running TV shows with no planned ending meet the fate of a decline in quality as the show goes on. Procedurals are best designed to go on for as long as the creators want, as they can likely keep drawing from real-life cases of medicine, law, etc. to fuel the plot. On the other hand, fictional dramas that carry on indefinitely run the risk of becoming repetitive or stale over time as the audience loses interest in whatever initially made it popular.

On the other hand, some TV shows were only ever meant to have five to eight seasons, but they still got worse each year. They managed to stay on the air due to a dedicated fanbase, but critics and even some fans were forced to admit that by the end, the show was not what it once was. Some of these shows would perhaps have worked better with no more than three seasons, while others were simply ruined by a terrible ending.

10 Supernatural (2005-2020)

Different showrunners and an expanding universe undermined Supernatural's story.

Supernatural got worse after season 5 in several ways, but the one with the biggest effect was probably the change in showrunners; Eric Kripke's departure meant a lack of horror influence from there on out. Several more showrunners with different visions came and went in the next 10 seasons of Supernatural, resulting in an inconsistent tone and story. The show also demonstrates problems with a repetitive plot and an increasing number of plot holes. While ratings stayed high in later seasons, audience interest dropped.

Supernatural is a prime example of a show that went on for too long because of what this meant for the world-building. There are only so many different supernatural crime scenarios the Winchesters can happen upon, leading to repetition. This, of course, includes the running joke about how many times they have both died on the show. Additionally, as the world's lore expanded, it started to contradict itself. The controversial Supernatural finale cemented the conception that the show had been going downhill for years.

9 Riverdale (2017-2023)

Riverdale became a supernatural mess after season 2.

The first two seasons of Riverdale are the best because they constitute a strange but enjoyable teen drama. The comics-derived characters are sleek and outlandish, driving a campy small-town murder mystery. However, around the time of season 3, the show started to contradict itself. The biggest and most disastrous way Riverdale did this was by introducing supernatural elements, completely changing the genre that the show's audience had become accustomed to.

Magic does not depart from the plot anytime soon but becomes more intertwined with it. Meanwhile, the characters aging out of their teens is also a change from how the show was originally pitched. The characters are inconsistent in other ways: Veronica's alternating dedication to and rejection of her parents is frustrating, while the couples that the audience rooted for in the beginning are shuffled around in the final seasons. Riverdale might have worked if it had stuck to semi-realistic teen drama, but it tried to incorporate too many things.

8 Heroes (2006-2010)

Heroes' bad later seasons are notorious in pop culture.