Both the computer animated Star Wars cartoons. The first season of Clone Wars is nearly dire, and the second isn't amazing either, but it steadily improves in every aspect.
Rebels never reaches the lows of Clone Wars (and consensus is that it doesn't reach the highs either, although I'd personally disagree), but the first season is definitely less serious than the rest, and like Clone Wars before it (which used a different art style than Clone Wars, meaning Rebels couldn't just use their art assets), Rebels looked better and better over time.
I would agree, though some later books (maybe starting around Carpe Jugulum, but also sometimes crops up in earlier works) felt less wacky -- and often angrier -- to me. Hence I stopped after Thud!.
The later Discworld books were definitely different than the mid-period books, but I just have to speak up for them here, because I see people say they aren't good and feel "off" all the time, and it disappoints me a bit. To be clear: I know you aren't doing that here, you specifically said they felt less wacky and angrier, not
worse.
The first couple of Discworld books are fairly decent goofy comedy-fantasy novels. They quickly bloom into something
incredible.
The last stretch of the books isn't incredible, but it's not stagnant, either, which I
really appreciated.
They aren't
as good, or as wacky, but they take the world he'd created and move it forward, and extrapolate what could happen in a place like that. Several of the characters have actually accomplished things, changed the world for good, and there are anachronistic things abound throughout the books. The later books consider what clever people with wacky magic and otherwordly beings might come up with in that setting. A fantasy comedy setting, where the author evolved the setting to develop a fantastic telegraph and postage system!
I also really enjoy some good righteously angry comedy, and so the slightly "tired of the world
still insisting on being so dumb about all this" tone was deeply satisfying to me.
Oh my goodness, the books' quality was like a story. Started at the low point, got more and more exciting, peaked, and then tapered off for an epilogue.