I wouldn't be surprised to find that the quality of the average cop in the US has improved since the 1960s, at least by some measures. But they are a lot more heavily armed, so mistakes and malfeasance on their part is deadlier.
The big thing that's changed is that you're hearing about it. The second biggest thing is that we've given cops more and more access to automated systems that they can misuse.
It's not like people having good reason to be skeptical of police is a new thing.