many fans and critics believe that after season 11 and the first movie, the series started to decline in quality. this was because many writers from the first three seasons seasons left (although doug lawrence, aaron springer, erik wiese and c.h. greenblatt still stayed). some of the later episodes were poorly received because the characters did not act the way they acted in the first three seasons. however, apparently, the show's quality improved once more after the second movie, when stephen hillenburg returned, until his death in 2018.