I don't agree with him when he said that season eight was odd. I mean, yeah, it looked a little weak compared to seasons 2-7, but that season was loaded with too many classics ("You Only Move Twice," "A Milhouse Divided," "Hurricane Neddy," "Homer's Enemy," "The Mysterious Voyage of Homer," "The Springfield Files") to say that it was the beginning of a new show. Season nine was where things really started to change.
But the way he broke down how the jokes were written back then versus how they're written now was spot on. The classic writers used to work until late at night every night to get the scripts like they were. They write jokes more like every other sitcom now instead of having that special uniqueness to them.