My point is that qualified immunity is not the problem. In your example, the cop should be prosecuted. Qualified immunity doesn't cover criminal prosecution, and a lack of prosecution has nothing to do with qualified immunity. Being able to sue that cop would be a nice bonus, but what you really need is for the cop to be criminally prosecuted for their crime.

Getting rid of qualified immunity wouldn't do jack squat to change that. The problem is an informal culture where police are not prosecuted (or if prosecuted, not convicted) for crimes.