Pfaff has pretty good data to back up his claim. He looks at legislation. He looks at mandatory minimums. Everyone plays their part, but prosecutors have a lot of power over sentencing. Plea deals play a role here.
And in many places prosecutors are politicians in a sense, because they are elected. One recommendation is to go back to appointing prosecutors rather than electing them.
So no, singling out prosecutors doesn't miss the point. It is an important point.
Yes, but it's become in the past couple years an out dated point in major cities (Boston, Philly, LA) where activist prosecutors attempting to prosecute fewer crimes and hand out lighter sentences are now being stymied by (appointed!) judges.
The problem with focusing on any particular role is that the other parts of the system will step in to force punishment.
And in many places prosecutors are politicians in a sense, because they are elected. One recommendation is to go back to appointing prosecutors rather than electing them.
So no, singling out prosecutors doesn't miss the point. It is an important point.