Why do people want to “Defund the police”?

Like I get that police brutality is bad, but police are also very necessary. Like, what are we going to do if we “defund the police”? Who will stop all the criminals? I don’t get why people would want to do this. It sounds like the dumbest thing I’ve ever heard. People also keep saying that “people who say defund the police don’t know what it means, it means to redirect their funding to social workers and stuff like that.” But then people are still like, “but when a dangerous criminal is in my house, I don’t want a social worker to show up, I want the police to show up, because social workers can’t protect me like police can.” So it sounds like, they just want police to have their funding taken away so they can’t afford anything good? I’ve been getting a lot of “I can’t believe you’re this ignorant and uninformed” and stuff like this, so then what IS the point in defunding the police? What did I get wrong?