You're likely to find a lot of fans believing that the show should've ended at Season Five, with the exact reasons varying from season to season. For instance some saying the Sera Gamble era (Seasons 6-7) was bland and overly forgettable with heaps of filler, and some saying that the Jeremy Carver era was messy, all-over-the-place with Story Arcs that had no sense of knowing where they were going and that it made Sam Took a Level in Jerkass.
- Season 6:
- The return to form approach pleased some older fans with its drastically pared-down cast and concentration on the Winchester brothers’ newest trust issues, but turned off newer fans.
- The season starts by hitting the reset button on the finale of Season 5, not to mention more than one plotline resolved in that or earlier seasons.
- The realization that Sam had lost his soul and the brothers’ attempts to get it back was planned to be the main arc of the season, but fan backlash prompted the writers to conclude it halfway through and introduce new storylines (Castiel becoming a villain, for example, was only thought of at the last minute as a replacement).
- The results were still mixed, among them being Eve’s introduction as a new, somewhat derivative Big Bad after more than half the season was already over, then promptly dying before the season finale to make way for Crowley and Castiel.
- Season 7: While Season 6 had its flaws, and definitely suffered from the loss of the original showrunners, this was where the show really started to show its age badly for some:
- For one thing, the Sam/Dean drama had become way overplayed by that point.
- The abrupt dropping of the very-promising-sounding Cosmic New Order at the beginning of the season (Castiel was going to be the new God, while Crowley was already the king of Hell) was also disappointing. The fans were pumped and excited, and one wonders what the writers were thinking when they threw it out, as Castiel and Crowley both vanished from the plot for some time.
- And who took their place? The Leviathans, who were a complete Ass Pull, and remained extremely vague in their abilities for several episodes. The writers themselves apparently couldn’t figure out what to do with them, so they had them disappear for long stretches of time while still trying to make them out to be this huge threat… except that their goals were completely undefined.
- Eventually, they had an episode where their leader becomes a Strawman Political Corrupt Corporate Executive so they could pull a Take That! against conservatives and libertarians, which only served to offend some of the fanbase.
- Then the Leviathans disappeared again for an even longer stretch of episodes. They weren’t doing very much onscreen, but Sam and Dean’s dialogue constantly exhorted the audience to remember that Vagueness Is Coming. The slow development of the Leviathan storyline resulted in a lot of filler episodes to boot.
- The fandom was also deprived of Bobby and the Impala for most of the season, resulting in further dissatisfaction.
- On the plus side, the Leviathans became more well-defined towards the end of the season. We also got the introduction of Plucky Comic Relief character Garth, and Castiel returned and developed further as a character, while Bobby got an impressive ghost-arc which tied up his character quite nicely.
- Season 8:
- Once again, the previous season’s cliffhanger – this time Dick Roman dragging Dean and Castiel to Purgatory with him – was resolved in the first episode of the season thanks to a Time Skip because Sam and Dean can’t be apart, ever.
- Dean and Castiel’s time in Purgatory was shown through flashbacks and were arguably the best parts but they were few and far between.
- Sam’s new love interest Amelia and perfect-life-while-Dean-was-gone subplots are near-universally reviled. His I Just Want to Be Normal speeches, along with his hatred of Dean's new vampire friend Benny, brought the Wangst to a new high.
- Crowley returned and appeared to be the Big Bad, though much mileage has varied as to whether or not he was any good at it.
- Perhaps realizing their mistakes, the writers tried to retool the season around halfway through, much like what they did with Season 6. Amelia was written out, the Men of Letters were introduced, and Sam was given a new story arc about him performing trials to close the Gates of Hell. Most Sam fans were happy, but Dean fans were frustrated about him repeatedly being pushed Out of Focus as his Benny and Purgatory plots were dropped.
- Regardless, the second half of the season was definitely better-received than the first.
- Season 9:
- Both Sam and Dean took respective levels in Jerkass, leaving Castiel as the only real sympathetic character on the show.
- Most of the show’s remaining supporting cast were either Killed Off for Real or Put on a Bus.
- The Myth Arc bounced around without any clear direction for most of the year. Characters like Bartholomew and Malachi were introduced and set up as major players in the angel war, only to be dropped shortly afterward (with Malachi infamously being killed offscreen after only a single appearance). Actor Jensen Ackles admitted in an interview that the writers were just throwing out ideas and seeing which ones stuck.
- Eventually, they settled on the Mark of Cain story, one of the more popular things to come out of Season 9… and then proceeded to do almost nothing with it until the final three episodes of the season.
- Not helping matters was the fact that the whole season was undercut by several lengthy stretches of heavily-disliked filler episodes, many of which (such as "The Purge" and "Alex Annie Alexis Ann") have been called by fans to be some of the worst in the show's history. There was also "Bloodlines", an ill-received back-door pilot for a spin-off that failed to come to fruition.
- Amongst it all, there’s the constant fighting between Sam and Dean, which is something that fans of both characters are getting sick of.
- Season 10:
- Once again, the show had a potentially amazing storyline set up at the end of last season - This time, Dean being turned into a demon by the Mark of Cain. And once again, that potential was completely wasted as the story was thrown out the window three episodes into the season because Status Quo Is God (noticing a pattern here?).
- The writers themselves seem to have realized how badly they dropped the ball there, as they spend the rest of the season awkwardly teasing that it could happen again, but because they failed to establish Demon Dean as particularly dangerous or hard to deal with, it feels like an empty threat.
- The attempts at expanding the cast with characters like Hannah, Rowena, and Claire, most of whom are Base Breaking Characters or worse, are reviled by many fans who want the show to focus on the older characters they're already invested in, and the lack of a central villain to fight - or even any real objective for the heroes other than just trying to find something to do about the Mark of Cain and hoping Dean doesn't go on a killing spree in the meantime - has caused nearly the entire season to feel like filler.
- Not helping are the deaths of Charlie Bradbury and Death itself and the finale ending with a textbook case of Vagueness Is Coming.
- On the positive side, the writers seem to have finally grasped how sick everyone is of the Sam vs. Dean conflicts and started letting them get along again, and there's also been a few hidden gems such as "The Executioner's Song", which is widely agreed to be one of the best episodes the series has had in years.
- Season 11: It initially showed an improvement on previous seasons. The writers finally managed to match the scale of Season 5 in terms of the threat. However, while the characters may have been on a grand scale (God and his sister), after waiting all season for the confrontation, the actual events were largely lacking in drama.
- Season 12, in a Broken Base kind of way. The child of Lucifer set-up is generally well-liked, but the Men of Letters plotline isn't that popular (although a few of its characters are), given how the eventual descent into feuding between the Hunters and the Men of Letters can feel like a frustrating, unnecessary Conflict Ball.
