Sakura is called useless because she is useless. Simple as that.
Getting back Sasuke is something Naruto could have sent a clone to help with. Kurama chakra reserves > Sakura's. Kishimoto had to make Sakura relevant for the final boss fight, so Team 7 could work together again. There's literally no other reason Sakura would be needed over Naruto. And there's no other reason Kaguya would fly straight up into Sakura's punch.
"B-but the Byakugan blind spot..!"
At the back of the neck. Not the top of the head. And Sakura's body is still larger than the small blind spot the Byakugan has. Kaguya was blocked to the left, right, and above. She still had backwards, forwards, and down as escape options but instead chose to go up. She also had the option of jumping dimensions again.
Naruto was alive after losing Kurama because Uzumaki. This is something already acknowledged in the series. Sakura's actions were not necessary for him to live. People need to stop fapping that. Uzumaki can survive the extraction for a period of time.
In regards to her abilities, Sakura is by far the weakest link on Team 7.
Medical abilities? Naruto can recreate body parts and stabilize the life force of dying people.
Strength? Susano'o, Rasenshuriken, and Tailed Beast Bomb all are far stronger than her "punch the ground!"
Genjutsu capability she "supposedly has"? Sharingan and Rinnegan genjutsu has it beat.
Diversity? Nonexistent. She has the smallest moveset of the team.
This is the character that forgot how to breathe. This is the character that stood frozen with a kunai in her hand while a guy was begging her to poke his eye out.
