Walking Dead.
Don’t get me wrong, I LOVED the first three seasons. Then, they brought new show runners in and they destroyed the show. The storytelling was insulting, there was no creativity, they immediately made our favorite characters so unlikable, events just happened for no real reason, and it just felt like these new writers had no prior knowledge of the show before working on it. I can only think about what this show could have been if these changes didn’t happen.
The end of the line for me was how they were painfully dragging out the whole Negan saga. I don't remember what season it was but I just quit in the middle of it