Sakura is not useless nor has she ever been in my opinion, she is just as valuable as the other team 7 members. She doesn't have a kekkai genkai like sasuke, and she didn't steal a scroll like naruto, nor is was she given a sharigan like kakashi
She has had to study,learn, and build her own unique skills form the bottom up. She should be given more credit for her hardwork, but everyone has an opinion.
Bit if we are going to go down the road of who was useful or not:
Didn't really have any major contributions to missions, fight scenes, or ninja skills. all I am saying is before people try to bash Sakura, there are other naruto characters that have some qualities that categorize them as not being useful.