The model worked back when episodes were self contained. I don't need to see seasons 1-20 (or whatever they're up to now) of The Simpsons to understand the latest episode. Old Star Trek was the same. You didn't need a huge back story. Kirk/Picard and chums were the good guys. The guy with the plastic on his face and angry eyes was the bad guy. It was easy.

But stretching a simple story over 10 seasons of gradually declining quality is nonsense. By their own logic we can only have a conclusion when the quality has declined to the point that nobody cares what happens. Might as well not even have an ending at that point.