Crime prevention does indeed start with social programs. But it doesn't end there. I'm all for defunding the police and I do agree that in the US police is really out of hand, but let's not be naive here. Social programs aren't going to address organized crime, or crimes of passion, crimes of immaturity (tenagers are both immature hormone soups and capable of causing harm) or political extremism. Antisocial behaviours can appear even in the socialistest of the welfarest of the welfare states.
Not to mention that cops have at the very least also the role of maintaining order, which is different from preventing crime. Think traffic cops, or rowdy crowd marshalling, or stopping disorderly conduct in public, or (extreme example) breaking up the mob that wants to lynch the alleged pedophile, to make sure he gets due process.
I'm all for a profound overhaul of policing, and for deep changes to what first responders are called for what emergency, but, honestly there exist functions for which police is useful.