Decline

Since at least the late 1990s, a general sentiment among longtime viewers is that the show has been in a constant state of decline and that the show's golden years-generally considered to be from the second or third season to the ninth or tenth-are far behind it.

Around the tenth season, many viewers and critics took note of what was perceived as the show's moving away from character-driven plots to more emphasis on zany antics and celebrity cameos (although guest spots have been controversial in the past; Julie Kavner and Harry Shearer having boycotted season four's "Krusty Gets Cancelled" due to the overabundance of guest stars). This left a feeling of disillusionment among longtime viewers and the belief that the show was quickly growing tired and drawn out. Al Jean, showrunner since season 13, has been the target of extensive criticism surrounding the show's quality over the years, with many staff members claiming the show was becoming too "sentimental" and jokes were being rushed out. Jean has responded with: "Well, it's possible that we've declined. But honestly, I've been here the whole time and I do remember in season two people saying, 'It's gone downhill.' If we'd listened to that then we would have stopped after episode 13. I'm glad we didn't."

Castmember Harry Shearer has been vocal about his perception of the show's quality, citing in 2004 his belief that seasons 13-15 have been among the worst, although Dan Castellanata has argued that the show has simply been changing formulas to stay fresh and relevant. Matt Groening has also defended the show's later years.