Officers standing at the corner, walking the beat, etc., may prevent all sorts of crimes without needing make an arrest. In fact, that's likely their most effective impact.
Which means that much of what prevent crime must be something more social, less crim justice.
Perhaps we should invest more in that.
The criminal justice system only snags a small fraction of cases, and that fraction shrinks significantly at every level.
But if we, say, focus on helping someone manage their anger or address excessive drinking, that effect operates all the time.
But still: unlikely that the CJ's low-prob random interactions are what really shape behavior.
Most social control is coming from somewhere else. Defunding is about emphasizing funding those (non-CJ) institutions/approaches.