Regardless, I agree that the dialogue is important and overdue.
"Do we expect a social worker to protect a child from an abusive parent?"
This already happens a lot. Often police can't do anything substantive unless there's a crime in action or some existing record. A social worker might be the only safe long-term presence around (and availability/quality of social workers is an enormous problem). Removing children from their homes can often put them in the foster system, which is also woefully inadequate and has funding/employment issues.
If it doesn't come from defunding the police, I think the major piece to take away from this overall conversation is that Americans are in dire need of better social programs that can better treat these things before policing is needed.
At the moment we have a weak mental health system and an overbearing policing system. It's no wonder our prisons are filled, our homeless have rampant addiction issues, and people are getting shot on the street.
It seems to me that cops/no cops each has its own pros and cons and neither is a clear "right" solution.
We definitely need more mental health support and less frivolous prosecution for things like drug possession and homelessness. Social programs would (hopefully) go a long way in addressing some of these at their root cause.