LogFAQs > #967383479

1 is underrated, in my mind. There were still a lot of elements that had yet to find their mark, but it was still a very good season especially with what was around at the time.
2-8 is the series at its best.
9 and 10 were still very good as a whole, but this was around the point where a number of episodes didn't hit and a lot of aspects that I dislike about newer episodes started seeping in regularly.
11-14 was where things started to notably decline, but it was worth checking out about half of the episodes. This was the point where they had resorted to more outlandish scenarios that felt like the writers were like "Hey, what if the SImpson family or that specific character did X, became Y, went to YZ and/or a certain thing from a previous episode involving them came back?" and it was nowhere as effective/funny than the material from the 90s.
15 onwards was when the show overstayed its welcome.

The funniest thing involving the Simpsons within the last 15 years is probably the Dark Simpsons YouTube channel and that is just re-editing old Simpsons clips to create a new narrative.