You can’t add more criminal laws to deal with systematic refusal by law enforcement to obey and hold other law enforcement officials accountable for obeying existing law, because that relies on the same people whose behavior you are trying to correct to auddenly behave differently to have any effect.

The US, in fact, has a comprehensive federal and civil and criminal prohibition applicable to such behavior (the prohibition on deprivation of rights under color of law and conspiracy against rights), but the criminal prohibition is consistently inadequately enforced, and the civil prohibiition has been neutered by applying qualified immunity against it, which arguably is inconsistent with the letter of the statute.

There's some truth to that, but I think that changes in such laws have resulted in slight improvements over time. Also, passing such laws at a higher jurisdictional level can allow comparatively "good" people at that level to disrupt local bad behavior like the stuff in the article. There are also other kinds of legal changes that can help, like transparency requirements and bans on certain kinds of police union contract provisions. More controversially I think there should be laws that shift the burden of proof (something along the lines of "every police officer is assumed to be unfit for their job unless they affirmatively demonstrate otherwise").

I think one thing that is needed is a "viral" kind of law that criminalizes essentially all attempts to perpetuate, conceal, aid or abet the underlying malfeasance. So that if you can get some people wedged in who do want to do the right thing, they can bring the whole house crashing down by convicting the whole network of corrupt officials.

Ultimately you're right though that there does need to be some cooperation from "inside the system". The question is just what can we do do lower that threshold.