Too many plot twists with each one trying to outdo the last is the same death spiral of adding features for the sake of developing something new. This is when your product has jumped the shark 🦈🦈🦈
At the beginning of a tv series, although the characters may have some initial backstory for credibility, the sitcom creators generally have free reign with the direction to take the plot and story lines. As the series progresses the audience learns more and more about the characters and the canon of the universe the characters inhabit becomes established. Script writers must acknowledge and build upon this history to gain fan approval and continued endorsement of the show.
At the same time, as the history of the show increases in complexity it becomes more difficult to think of new ways to engage the audience - what is believable can also become mundane or lame. the baseline moves.
It becomes harder and harder to preserve the existing experience which created the fan base in the first place while also continuing to surprise and delight. When a TV series goes so far in trying to create the wow factor that they neglect or cancel previous canon, critics will describe this moment as jumping the shark (based off the episode in Happy Days when Fonize jumped over a shark while waterskiing).
Anyone familiar with the Kano method will recognise how sitcoms fall in to the trap of trying to outdo every previous episode where what was previously “surprise and delight” has now become the “must have” baseline (I’m looking at you 👀 Married at First Sight and every other reality show on the planet).
Products with an established fan base have a canon and a history with their users. They need to maintain the baseline but at the same time continue to surprise and delight users. Trying to maintain this balancing act as time goes on is like continually adding plot twists to a sitcom.