He’s saying let’s analyze the work they do, find alternatives for those roles, and _then_ reduce the scope of the police force.
Defunding seems much less important and farther down the road than making their jobs achievable, and the rest of us safer.
There are secondary effects too, though. The police force competes for funds with other public infrastructure like schools. Defunding the police means we can allocate that money to more productive and less violent causes.