People are already leaving Seattle, Minneapolis, New York where they're defunding the police.
Lots of new Detroits on the horizon.
As far as I am aware, defunding the police is meant to be about rechanneling the money saved into multi agency community work in poverty hit areas, and therefore reducing the factors that cause crime in the first place. Have a look at the Glasgow example in the 00s if interested as it had a good impact on reducing crime. If you simply defund the police and nothing else, then of course it won't work and would be worse.
I suppose it could be worse.
BLM UK (as opposed to BLM USA) want to abolish the police completely, and close all the prisons.