The interesting thing is that two of the most remembered jokes from the show, "Serenity Now!" and Festivus, were both in Season 9.
I don’t think seinfeld was great for jokes as such. if anything, I feel like later episodes were a bit trying too hard to create jokes and over-the-top silly situations (e.g the episode where Kramer sells the real Peterman bus tour and Elaine trying to dump the stumps of the cupcakes)