I still can't stop but think how stretched out the Hobbit films were, for an otherwise short book. That's a sin that stains forever with me. The Lord of the Rings films, do have their own flaws, but they're fairly contained and can be debated as to whether they were good or not. I have so much trouble excusing anything with the Hobbit though.
And I hope we never, ever see anyone tackle The Silmarillion. Simply because, there will be so much improvised fluff in that would-be film, that it'd make the Hobbit films blush.
The One Punch Man anime turning into One Frame Man in its third season.
From battles consisting of transparent PNGs sliding from the bottom left to the top right corner of the screen, to ludicrous censoring techniques like replacing a cigarette with a lollipop.
For the fourth season they just inversed the poster from the third season. Tbf it will be actually Season 3 part 2, but it shows they aren't even trying.
Juxtaposed to this is the Dorohedoro anime, that also dropped a new season this year, after six (!) years.
The long wait had a good reason. The animator loves the manga, but was busy working on the Attack on Titan anime and didn't want to rush Dorohedoro's second season. It's a huge improvement over the first season, refining its mix of 3D and 2D hand drawn content into a wonderfully horrifying experience.