How do you know they aren't making a dent in the numbers? You don't know, and can't know, the counter factual. One anecdote though, police are doing less policing right now in cities like Chicago, and the the outcome is not looking good.
At least 106 people shot, 14 fatally, in Chicago weekend violence
It's pretty easy to say when your stats are 10 times worse than a similar developed country and look more like a developing country where warlords are in charge
Or, in US police is at war
Which is equally bad
EDIT: to give more context
If poverty rate in US was worse than in Nigeria, people would say that something went horribly wrong
Homicide rate in US is actually 1.5 times worse than Nigeria and two times worse than Uganda and Congo
At least 106 people shot, 14 fatally, in Chicago weekend violence
https://www.chicagotribune.com/news/breaking/ct-chicago-week...