At this point, I'm fairly certain that it's a pipe dream to assume that it's possible to "fix it" without serious sustained effort (which costs some money obviously) and without also drastically improving the adjacent systems (as you said also). Sure, we can call it social services, but the goal is to really reduce both crime and police brutality.
It's a complex problem, but very simply the funding issue is that militarization was cheap (because military handed off a lot of things for cheap/free), and any and all social service thing got more expensive simply due to big "external" factors like the Baumol effect (human labor is relatively getting more expensive compared to anything that benefits from capital investment, ie. industrialization, mass production, technological progress), the Southern Strategy culminated, War on Drugs revved up, social polarization increased, inequality shoot up, these all led to more crime, more tough-on-crime programs, more people in the criminal justice system, and that's a lot more expensive. And of course reintegration and related social programs got worse for the same reasons.
See also https://www.slowboring.com/p/fixing-the-police-will-take-mor...
This is an interesting wrinkle. I would hope that addressing the corruption that enables NIMBYism would also affect the viability of organized crime.
I disagree that law enforcement is underfunded. Public services which would reduce the prevalence of crime are absolutely underfunded; law enforcement is not one of those services, as it currently receives enough funding (and more) to carry out its part in crime-lowering efforts. Fixing its mismanagement means funding separate institutions dedicated to oversight, for example.