I haven't gone through 17 pages of comments, so apologies if I'm repeating what someone else has mentioned.
I'm a bit disappointed that Kishimoto stopped the flashback where he did.
The next moment was Sakura saying that the one thing she hated was Naruto.
That would have been a nice contrast to the present, seeing her with a hand on his shoulder and fascinated by what is new in his life.
The other point is to remember that we are getting Kakashi's opinions.
He is an "unreliable narrator".
He has *always* been about Sasuke, to the point that he pushed Naruto's training onto others and completely ignored Sakura (who had to find a real mentor in Tsunade).
Of course Kakashi is going to focus on Sasuke when thinking about Sakura's past.
It is more important when more objective observers, like Yamato and Sai, mention the importance of Naruto when talking to Sakura about her feelings.
People give Kakashi too much of a hard time for the one time he trained Sasuke instead of Naruto...myself included, But if you think about it, it was the right choice to make, Naruto was facing a ninja from his own village and a genius at that, Naruto was going to loose, but atleast he would be alive, where Sasuke was facing a ninja from another village who left one of Konoha Ninja's in a career ending injury, and killed a team of Ninjas who tried to attack them during the chunnin exams, Sasuke was going to loose, and it would likely end with his death. Also just before he started training Sasuke, Kabuto had made a play at Sasuke's life so Kakashi was a bodygaurd as well as a teacher for that month.
We don't actually know how long Kakashi had with the team either, it could have been anything from two to six months. Then after the exams, Jiraiya took Naruto to find Tsunade and after his failed fight with Itachi and recovering in hospital he had to go on multiple high paying solo missions to help the village recover from the damage, and then Sasuke ran away and within a couple of days Jiraiya toKaok Naruto off on his training trip, and Sakura convinced Tsunade to train her. People often forget the Manga timeline and concentrate on the real life time line or the Anime timeline. For example the past 150 plus chapters has only taken place over two or three days, Naruto said it would be his birthday tomorrow months ago and it's still not arrived yet.
Kakashi is not a unreliable narrator, he is usually semi-correct, like when he said the Uchiha clan came from Hyuuga. Kakashi or Yamoto, are often tools used by Kishi to give you hints about, Kakashi just gets a bad rep because allot of his comments came in the first part of the manga and you get the feeling that Kishi made quite a few changes to the story for the second half and his mouthpiece Kakashi got made to look like a idiot.
If you want to talk about poor teachers, we have yet to see the results of Jiraiya's two and a half years of training Naruto. Sakura got to a point where she was getting close to equalling Tsunades level, Sasuke learnt plenty of Jutsus and defeated an entire platoon, and learnt how to combine his two elements, Naruto learnt how to make a bigger Rasengan and I'd argue got weaker because Jiraya weakened the seal so he started to rely on Kuramas power more and more.