I've seen in the military where good leaders can turn around an organization very quickly. It can happen in police departments. From the data I've seen, it looks like accountability is one area that needs addressing. Perhaps independent committees to review complaints would help.
Military personnel are generally removed from their local community, broken down, and rebuilt as the military sees fit. The goal being to develop professionalism and an espirit de corps.
The police are not military, nor should they ever be. They should wear blue, not black or camo. They should drive clearly marked bright ass emergency vehicles, not darkened tacticool crap. They should be closer to firefighters than to the military. Every unholstering of a gun should be treated as a very serious thing. Taking your AR-15 out of your cruiser? Even more serious. Body cams and dash cams should be mandatory, with automatic, serious penalties for not being able to furnish footage/tampering with the cameras.
Cops ultimately need about 3x more training before they are allowed to be out on the streets, with the majority of it being in practical de-escalation. Then you need to absolutely nail anyone that violates the public trust with serious charges, including automatic escalators for being a public official. I wager just those two things would cut malpractice in half, if not more. They also need to look at policies involving petty misdemeanors, because those are almost always used as a pretense to selectively harass certain communities. You can bet a majority of those laws would not be on the books if they were enforced consistently.
Most countries with model police take 2+ years to train them. The U.S. standard isn't even close to that. We're not even really training these folks to begin with and then not supervising them or giving them a real reason to behave. The end result is as expected.