Television

Possibly cheating, because anime, but Shokugeki no Soma (Food Wars). Initially a series following the protagonist as he entered a school where every dispute was settled with a cook off between two students (and sometimes a teacher). This seems over the top, but the food was always solid (they had a consultant just for it) and felt like something you could make with the right skill and ingredients.

In the final arc, they toss this all out to introduce a villain who can steal a chef’s signature dish/technique (something that is supposed to be unique to that chef) he gets a hold of their knife after winning a food battle. And he can wield those knives in any combination to form new dishes no one else can do. Just because. Also the dishes get less interesting in general, because it’s about powers related to cooking and not the food.

Arrested Development

supernatural, After krikpke left season 5, it just went in a totally wierd parasocial/sexual direction with the fans. and basically it was filler ever 2-3 seasons, til they finally ended it. and then Jensen tried to sneakingly with his wife start a new series behind jared's back which cause a whole drama situation going on. being both producers, you and your wife was pretty deliberate in not acknowledging jared or misha(he dint make a big stink about it, because he saw the fallout of jared and jensen and dint want the same problem to arise).

ISAIP, this series was on life support after 11-12, they also got too old physically, plus the plastic surgery is pretty obvious at that point. the actors are clinging on this for dear life, because they arnt hollywood material outside the show, hence why MAC is so wierd now(the actor) outside the show.

nutrek shows, not even based on continuity or the original intent, and that was verified by Kurtzman who had no interest in the lore, he was much like Les moonves with ENTERPRISE.

SGU, YEA they shouldnt have started with the drama at all, shouldve done like sg1, in between seasons or mid-season to help break up large plots.

Riverdale

sandman, it was pretty obvious how cheap the props and costumes are, so you can feel the cheapness, some people had problem with the characters not being what they are suppose to be for the comics. Lucifer, REMIEL. its probably NETFLIX squeezing whats left of the series before cancelling it, i heard neil gaimans sex perversions dint overall affect the cancellation of the show, it was netflix being the usaul, season 2 cancellation theme.

Community is the only one which comes to mind.

A lot of shows that begin with a mystery or quest to find a certain character or place, and then they find it in the first season finale... when season two starts, you realize whoever came up with it had no idea where to go from there.