I didn't believe you, so I looked up those cases. While there's a little more nuance to the cases than your summaries, you are pretty spot on. We are all cursed with this disgraceful knowledge now.
They have no legal obligation to be useful, let's put it that way.
There are cops and departments which take an active and sincere interest in community policing and social justice.... but power tends to corrupt, and the almost complete lack of obligation or oversight combined with the weird hero-worship of the right-wing means most cops and departments are not interested in anything except the perpetuation of their own power.