1v1 combat skills are key when in fight. I agree that she is essential to the story, but let's look at a combative.
I believe she could beat Kiba, TenTen, Rock Lee, Ino, and Tenmari easily. We can debate Choji and Shino but I feel she would beat Choji and lose to Shino, but I could see her losing and winning both of these
Her possession of attack type ninjutsu's are weak. She can not do a Substitution Jutsu at all, a key part of the fighting aspect to deceive your own opponents. She has no deception type jutsus. Compared to a character liked Naruto, who had Shadow Clone and Sasuke's substitution jutsu. While she can hold her own strategy wise, she would be much more of a lethal fighter if she had the knowledge to one of those jutsu's. Her strategy would be much more effective. Someone with a weaker jutsu based like Shikamaru could beat her due to strength.
Sakura only has two releases, Water and Earth. As a combat, she is no greater than Choji with her releases. Hinata has 2 plus the Byakugan, Shikamaru has 2, but he's such a genius that he would win. Kankuro would defeat her with his puppets, because he is obviously become a better puppeteer and can maneuver around Sakura. She can not just charge aimlessly and expect to win against the strongest opponents. It takes a strong jutsu to take out Hidan and Kakuza, and there is no way she would beat any of those two by brute strength. Naruto nearly died doing so by just his normal form. Sakura's ninjutsu battle techniques are too aggressive to take out ant Akatsuki besides Sasori.
Her strength comes after the battle, in her ability to heal others with her chakra control. That is where she is effectively the most useful character. Combat is not her strong point. There is nothing wrong with that. She is still useful after the battle.
In battle though, her abilities are a somewhat smart battle technique, immense strength, and healing. You can't heal immediately after battle, and even so, Naruto also has a healing ability as well.
Obviously she was with a team of Naruto, aka the strongest ninja and Sasuke, the owner of a Rinnegan and Sharigan, so of course she gets outshined, her use is in after battle, making Team 7 the most ideal for her circumstances. If she were placed on any other team, she would not be a character of interest at all. Fate had it's hand for her. If she were not a team with Sasuke and Naruto, she would not have the drive and motivation to try to master Medical Ninjutsu. SPOILER ALERT RIGHT NOW SO DON'T READ UNDERLINED, if the Third Hokage did not die, or Jiraya accepted the offer as the Sixth Hokage, the story would be much different SPOILER ENDS NOW
Sakura had a lot of fate play into her hands. I give her credit for using that fate to become a successful healing ninja, but there are a lot of factors that went into Sakura's usefulness as well