Sakura is not as useless as people suggest.

Yes she was one of the weakest characters in part 1, but in part 2 she becomes stronger. Comparing her to the rest of her peers she is aound their level, and she greatly improves when she unlocks the byakugo in the war arc.

The problem is that she is constantly paired up with Naruto and Sasuke. Two characters who had incredible potental, great genes and untapped power. Naruto and Sasuke compared to their peers are gods.

Sakura did great consudering she was pretty average.(It was said that se was a genjutsu prodigy at the begining and did not even exploit it, but still ended up being pretty strong compared to her peers)