Because, he's the reason Naruto is a mediorce manga and everyone and their mothers wants him to get owned by Naruto. Because Kishimoto jumped the shark and decided to make Naruto more stuish as Sasuke is more popular than him and hates that.I hate Taka Sasuke. I seriously consider him one of the worst characters or the manga among the characters who still matter. Ino or Sai are probably worse. But they hardly matter anymore. On the other hand Sasuke is very central character.
I won't even adress the fact he spams MS and fights like a retard.
Until Hebi Sasuke he was still my favourite character.
We can agree or disagree many things about Sasuke except his relevance as character. He had his own backstory built in terms of character relationships and themes that weren't related at all with the main character.
Sasuke was designed as rival of Naruto. But at the same time he was his own character with his own theme or motive: revenge.
Revenge constitutes everything that drives this character. We can agree or disagree if this theme was cliche or if Sasuke methods were justified or not. In fact many of the great debates in this forum born from that notion. Kishimoto always allowed room for that discussion. Regardless what you feel about the theme of revenge or if you dislike or like Sasuke we can all agree if something it's cliche it still could OR SHOULD be well developed.
One Piece, Kenichi and other shounen follow many cliches formulas but they give their own flavour and remain consistent.
So here I will adress my first reason I dislike Taka Sasuke.
1-What was crucial to Sasuke's character was the dichotomy between his goal and his method.
Kishimoto never said Sasuke's revenge per se was wrong. He never questioned the moral ground of Sasuke for wanting revenge. He questioned the methods and consecuences. That's why Kakashi said "stop your revenge... it will make you feel empty at the end". He isn't saying Sasuke wasn't justified... but at the end it won't bring him happiness.
This allow certain readers, fans, etc to make a connection with the character for good or bad. We know this kid suffered a great loss.
It's the weigh of that loss enough to justify any method?.
That was a question every reader had to answer. Our reaction towards the character would be a consecuence to that answer.
Taka Sasuke doesn't even leave space for that question. Kishimoto turned him into the Avatar of Hatred in order to justify his next fight against Naruto. Kishimoto destroyed all moral ambiguity in the character that set him apart from a villian and practically turned his goal and his method into something so childishly evil that doesn't left room for debate anymore. Before his fight with Itachi Sasuke was basically character-driven. He acted for good or wrong in terms or his convictions. That's why Sasuke could be ready to kill Naruto and at the same time try to save Oro's prisioners without any gain. That's why we could get different kind of reactions from him instead HATREEEEED like he was Nemesis from Resident Evil 3.
Kishimoto himself took a bit of time to react to the changes. For example making Taka Sasuke pulling an Amaterasu of friendship to save Team Taka AFTER ITACHI'S REVELATION. Yet in the next arc that involved him he was impaling Karin and laughing about it. What kind of character development is that?. It's not so much about Sasuke turning totally evil really... but it was so bad developed that is pathetic. If that was intention all along Kishimoto should spare us from comments like "I won't follow Itachi footsteps" and should focus from the beginning of Part 2 into following Sasuke slow descend to the darkness.
Instead of that what we get?.
Madara: Some random 3 elders ordered your brother kill your family. By the way... I took part in that too... but you shouldn't care too much.
Sasuke: HATREEEEED.... I'm the avatar of the elder son..... I'm gonna rape Team Taka even if that wasn't my style 30 chapters ago.
Hebi Sasuke hardly wanted to kill someone for pleasure before. Itachi was a duty. He tried to kill Team 7 only because he felt they get in the path of his revenge and to cut his bonds. But he never went on purpose trying to kill someone who wasn't directly implied in his revenge. We have the example of the 1000 fodders he defeated training with Oro, sparing Oro's experiments, saving Taka members, avoiding to kill Deidara, etc. Now Kishi pulls this shit he want "everyone felt his hatred... and turn his laughs into screams and crap" He completely changed his mentality.
Taka Sasuke was ready to spare DEIDARA who is more related to the evil Itachi represented by virtue to been partners in the Akatsuki... yet right now he wants to kill little girls, old men, women, etc that hardly were related with what Danzo and the other 2 elders did just for the lulz?.
Which brings me to the second point....
2-The target of his revenge.
We all agree that a good revenge story should have a memorable target.
This what pre-retcon Itachi represented.
1-The brother of the victim
2-Betrayed his trust
3-Appeared as an super powerful and invincible villian (at last in Part 1... I'm just talking the way he was introduced).
All this elements constitute a good drama. While I didn't like Itachi turning into a "dood guy" this development could have been better if was introduced at the end of the manga instead killing him in the middle leaving an empty Sasuke who was turned into a plot driven character to hype Naruto.
I don't like Itachi. But I admit among all characters there isn't one with the potential to enhance Sasuke's theme.
Itachi always should have been Sasuke's final boss. Killing him so soon was a mistake in my opinion.
Seriously who is Sasuke's target right now?. 3 random elders that hardly were developed during the series and Konoha villagers.
One of the main questions of the series was if Sasuke would be able to fulfill his revenge. Now this question was destroyed. What is his target seriously?. He already killed Danzo who was the main instigator against Uchiha. What this mean?. He completed 16% of his revenge or something?. There is no sense of completition anymore. Regardless if Itachi was good or not this answer and his fight should introduced at the end to close Sasuke's story.
There isn't so much drama between random elders and villagers compared to Itachi who was directly related to Sasuke, shared a backstory, a bond, etc... "Oh I'm gonna kill fodder number 392...." who ****ing cares?.
The only way to fix this a little would be if Itachi never killed the Uchiha at all and all was done by Madara instead just "helping him"... and even then it isn't a comparable bond. Besides Madara was already hyped as Naruto's final villian.
Maybe if Namikaze or Uzumaki clan were directly related to Uchiha's massacre.... nah... nothing with fix this crap anymore....
At this point I'm just interested in how everything will end and if Madara will provide more lulz trolling everyone. Sasuke has turned into a horrible character... not just for his haters... but for everyone who doesn't keep deluding himself. Probably it's consecuence of the whole manga going down into the toilet (Naruto turning into a messiah for example or secondary characters turned into Gato's samurais in terms of relevance) but at last I was hoping if Kishimoto would sacrifice the whole manga to develop a theme he would put more effort. Otherwise bring Ino and made her kage level.