MJF was fine as champ until he turned face, at which point he basically became the Youngest Buck in terms of the style and nature of his work, just absolutely insufferable winking, nodding bullshit. The company was in a secular decline/stagnation/whatever before he won the title, and to the extent that his reign hurt the company, I think it’s because A) he and Tony allowed the top title to become a barely-present prop in a midcard comedy tag team, and B ) their plans got scrambled like 6 times. He was clearly supposed to win it from Punk, then that didn’t happen. He was clearly supposed to resume feuding with Punk when Punk came back from his injury/suspension, then that didn’t happen. He was supposed to have a one off storyline with Adam Cole, that got weirdly over. That was supposed to bubble for a while, then Adam got hurt. Then MJF got hurt. Bad decisions and bad luck all around.