To be frank, Sakura’s character is fine as it is. It was never a problem. It is when there is biased double standards comparing her to Hinata is my issue with the whole thing. Would I like to see Sakura in action more? Sure but I never expected too much out of it and what we got is fine.
If I had an issue with her, it's on her use. Kishimoto seemed to really struggle finding ways to keep her involved in the plot. Naruto and Sasuke were Part of Team 7, but the core conflict of Part 2 wasn't about Team 7, it was about Naruto and Sasuke and Team 7 one aspect of their lives. I She cared about them too, but she wasn't part of the metaphysical aspect of their conflict. Kakashi's experience and mentor-type status as well as Obito being one of the final villains kept Kakashi involved, but she really didn't have anything like that either. From a strategic standpoint, having her as a medic was a good idea because in their like a work having medical assistance on site would be invaluable, but it didn't integrate well into a series were combat prowess is often a currency to relevance, especially in Part 2 where be able to fling the biggest jutsu became more and more important. It also didn't help that rather than focused missions that might has multiple fights scattered over the course a mission (like the wave arc), it became more like DBZ in nature.
As far as Kakashi training her, I can't recall what I may have through in the past, but now its far more a writing issue than a Kakashi issue. You can make an argument that he sucked, but its clear that Kishimoto was not meaning to convey or even imply it as there is nothing from Sakura that suggest she saw it the way many fans did and as Bail said, its clear off screen training occurred and Kishimoto just never really followed up on it.
It also clear, that by this point he had decided on them having them having individual mentors. People have criticized Kakashi for his treatment of Naruto, but I think Kishimoto just wanted him get set up Jiriaya. The point wasn't supposed to be Kakashi sucks, it was how do I get him to meet Jiriaya. In the process he makes a classic show don't tell mistake. I think in universe Ebisu is supposed to be a legitimately good instructor who is a poor fit for Naruto, but his treatment as a joke character while on screen undercuts this and got Kakashi accused of blowing Naruto off. We only know Ebisu is good because the series says so, the only two people who work with him on screen chafe under him. I've also come to appreciate why Kakashi would focus on Sasuke. He was facing a murderous sociopath who had tried to kill an incapacitated opponent. As awful as Neji was to Hinata, Gaara was worse and Sasuke possessed no method of getting past his shield without Chidori. From Kakashi's POV, what move did Sasuke (at the time) possess that would allow him to even damage Gaara? He didn't have Lee's speed. Without Chidori, Sasuke really didn't have the skill set to take out someone as tanky as Gaara was. I think he should have done more to make sure Naruto was more prepped, but Sakura had no upcoming matches and I think it works both ways. If she really wanted additional training during that time period, she could asked for it.