truthfully- I get your point- however, the biggest reason people call Sakura useless is not even related to Part 2 Naruto. Part 2 Sakura is obviously competent ( however with private Sanin tutoring who wouldn't).
-I imagine alot of people still remember part 1 Sakura. The girl who definitely was useless, arrogant, and downright mean to the protagonist. Sure, Naruto was a brat- but atleast when shit hit the fan he acted ( zabuza, Gaara, etc...). Remember Sakura vs Ino?
The only version of Sakura that was "useless" is part 1 sakura- however even to this day people don't forget how useless she was as a kid.
For me, I never disliked her because she was useless ( in part 1) even though she was- I disliked her because of her personality. She talked alot, loved Sasuke like a idiot, and was generally a hindrance.
So, besides from hanging on to the idea of useless Part 1 Sakura- I doubt anyone truly believes she is a terrible ninja currently. Its just that her sucking so bad for the entire part 1 of naruto kinda stuck around in peoples head and its hard to let go. For long time Naruto fans, Correlating Sakura to useless is almost a reflex.
-However, I feel that the real reason Sakura is bashed had nothing to do with ability, past or present. It has to do with character. People exagerate sakura's lack of skill because she is unliked by most of the base. I agree with them, I think sakura is a fairly terrible person, and I typically don't like it when she gets panel-time.
Since part 1 she has gained competence, however she has yet to let go of her annoying personality. Let me explain.
Why Sakura Sucks-
I felt like strangling her when she blatantly lied to Naruto ( trying to manipulate his feelings). thats such a ***** move. I doubt I will ever tolerate her, due to this event. Not only that, but even after lieing to Naruto, and poisening her comrades, she is unable to stab Sasuke. Furthermore, after being saved by naruto she ended up poisening him- which if a battle actually happened it would have caused his death.
During the juubi battle- I saw she improved- I thought I might actually like her- then she goes on and gets cocky as hell saying that she caught up to naruto and sasuke. So, she gets a little bit of power? that has a two year prep-time and she thinks she can tussle with naruto and Sasuke?- right after saying how she caught up- she needed saving- Right after saying she caught up to Naruto and sasuke- she goes right back to the sidelines...
I really don't care how strong you are- or what powers you have- ultimatly- I could care less if Sakura becomes a juubi jin- I still won't tolerate her.
- She can be the strongest ninja in the verse and she still won't have the mentality of a ninja. She still won't meet her goals, she will still be a *****, and she still won't be able to endure.
Being a ninja is about enduring, Naruto, Sasuke both endure. Sakura has had multiple oppurtunities to showcase her character but every time she screws up!!! Enduring is fighting a superior opponent, knowing you will loose ( hinata vs Pein) What does Sakura do when she see's someone stronger? that's right she stops breathing.
People don't dislike sakura because she is fodder ( she isn't, she is actually strong for her age) they downplay her because of her abhorrent personality.
Edit- For those saying she has great control- you do realize that one of the biggest reasons she has amazing control is because of her puny ( I mean miniscule) reserves. It was established early part 1 that less reserves means easier chakra control.
basically,- Sakura was a natural at chakra control because she had tiny reserves. Considering that Kyubi Mode Naruto has much more than 100x her reserves that means chakra control is 100x harder for him atleast!!..... --- Really takes away from her "perfect control" doesn't it??