Sometimes it feels like the culture of American policing and criminal justice is so broken that we just need to start over from scratch.
The defunding movement hasn't been well-explained in the press, but the actual core reality is that police unions need to be removed, and to remove the police unions, you have to start over with new police forces.
There's 4 problems that need to be solved first though:
1) After you start over, how do you prevent a new union forming?
2) In the USA, District Attorneys (DA's), etc. are elected. To get elected, police union support at election time is needed/helpful.
3) How do you move existing court cases ahead after you fire the arresting officers?
4) Even though police officers often have misconduct, the DA needs their testimony to be believable for cases. So the misconduct is generally suppressed from public view.
As you can see, the dependency of DA's on police officers alone makes this issue very difficult to solve, and when combined with unlimited legal aid from police unions is insurmountable.
Canada, which operates quite differently than the US (DA's are appointed), also has a problem with police unions stonewalling investigations. The officers involved just remain silent and lawyer up, the same as the US.