#1 Forgetting the point
The premise of Sayonara, Zetsubou Sensei is controversial to put it lightly. It tells the story Nozomu Itoshiki, a young teacher who desperately wants to end his own life. The opening moments depict him hanging from a sakura tree, only to be rescued by a girl who is later revealed to be one of the students in his new homeroom class.
Nozomu is intelligent and charismatic, but deeply pessimistic. Even the smallest setbacks in life spiral him into despair, and he’ll frequently rant about his bleak worldviews to his students. He even forces them to partake in bizarre exercises, such as asking them to identify the failures in their lives as a depressing alternative to a “spot the difference” drawing. It’s a great premise that carries the series well throughout season 1, but the story soon loses its edge and that leaves SZS with little to fall back on.
Subsequent seasons don’t even really address suicide at all. They joke about Nozomu being negative all the time and make sure to include his wacky catchphrase in every damn episode, but nothing in seasons 2 or 3, nor the OVAs and specials, ever meaningfully continued his character arc. At one point the show just suddenly turns into a toothless comedy series about an eccentric group of high school students and their weird teachers. Wow, we’ve never had an anime like that before!
#2 Shallow characters
This process of losing complexity and becoming a more generic character is a faith Nozomu shares with most of the cast. Class 2-H is filled with bizarre characters that seem interesting in their introduction episodes, only for their development to stagnate. Their personalities are then dialed back over time until they have nothing left aside from some easily-recycled gags to pad out episodes with.
Kimura is a good example of this process. She is first introduced as a returnee student who takes great offense to Japanese customs and is very confrontational, both towards her peers as well as her teacher. This is given a twist in the form an alternate personality, in which she is the perfect idealization of a Japanese woman. The show calls this a bilingual personality, but the idea is ditched immediately. She never switches again throughout the show and her temper is dialed back significantly. By season 2 & 3, Kimura just exists for a running gag about pantyshots.
Watching the characters degrade like this really bothered me, because I honestly enjoyed a number of them when they were first introduced. I was curious how the reclusive Kiri would fair after finally leaving her home or how Matoi’s stalker tendencies would affect Nozomu’s life going forward, but none of this ever goes anywhere. The girls are just kinda there to react to the plot and partake in jokes, most of which don’t have a lasting impact or connection to them.
Adding to this frustration is the show’s insistence on including characters that don’t have much going on to begin with. Nami is an obvious example, with her personality being based entirely around the idea that she’s as plain a character as possible. Other characters that fail to stand out (for less deliberate reasons) include Harumi, who is just a standard Fujoshi character, and Ai, whose whole deal is that she’s pointlessly apologetic. Those would hardly count as extras in any other series, but here they feature prominently in almost every episode.
#3 Drab, cheap visuals
Sayonara, Zetsubou Sensei came out in the aftermath of Hidamari Sketch, during a time where both Shaft and Akiyuki Shinbo began to shift towards becoming iconic for arthouse anime. Calling this anime a proto-Monogatari is tempting, but it would also severely oversell the quality of SZS‘ art.
The anime features a lot of visual elements that would later be used in future Shaft/Shinbo works, but overall the anime is very shoddily put together and bland. Characters look simplistic and frequently go off-model, much of the animation is static or set against barren backgrounds, it’s not very pleasing to look at. The few times where the show runs wild with its visuals tend to be fairly short and unimpressive, certainly when compared to Hidamari Sketch, Madoka Magica, or Monogatari.
#4 Teacher x Student romance bait
For all his flaws, the students of class 2-H really do adore their teacher. Some of them a lot more than is probably healthy. This gives rise to a romantic competition between several of the students who are looking to seduce poor Nozomu, in spite of his clearly stated indifference to them.
It’s just kinda there for no real reason. None of the students have good chemistry with Nozomu and it feels like the writer didn’t actually intend to push this story forward. It’s there and it’s sometimes referenced, but no effort is made to actually progress any sort of romance. This persists all the way until the final OVA episodes, at which point the whole deal is officially left inconclusive. Very typical of the series a whole, but still a disappointment after being constantly teased with a resolution by the anime’s OP.
I am aware that the manga has a very different ending. I don’t really care for the direction it took either, again because the characters are too shallow, but it’s at least an actual conclusion with a unique idea to it. Sadly the anime never adapted it and it’s now been 9 years since the final installment.
#5 Repetitive formula
The anime follows an episodic format with storylines that largely exist to poke fun at social constructs and the trappings of modern society. I’d be lying if I said that the satire isn’t occasionally on point; I certainly enjoyed a number of episodes, but the show as a whole felt too stagnant.
The motions are usually the same. Something happens to one of the students that sends Nozomu into a rant about society or life, he expresses his despair, Kafuku pops in to raise a counter-argument, and from there a storyline unfolds exploring the concept at hand. These ideas are sometimes creative, but it frequently felt like the show was repeating itself, either by addressing comparable topics or using the same format to explore it. For example: several different episodes take Nozomu and his class to a surreal locale, like a spooky part of town or a mysterious tower, where they witness several examples of a social norm taken to its extreme.
Even when she show isn’t outright repeating itself, none of its episodes ever felt particularly amazing. The series has its moments, but its peaks don’t rise far and only two scenes I would describe as “memorable”. Compare that to another episodic series like Space Dandy and it’s not a good look at all.