Concerning Police in the present form in the USA. "It is impossible for any entity which actively participates in forcibly taking your money on an involuntary basis (government empowered Police etc) to also be the thing which will protect you from people who would rob you of your money. " Police are funded thru confiscatory measures, so the foregoing statement is axiomatic. Meaning it's the fucking irrefutable truth.
Concerning private security. Every person has the right to defend themselves or hire others to do it on their behalf. This is a demonstrable natural right. Just ask yourself, if it is right to attack people who aren't attacking you or if others have a right to attack you when you aren't attacking them etc. and the answer will be obvious.
Therefore, we can assert, "No person(s) has the right to use offensive force and every person has the right to use defensive force."
Offensive force is the initiation of force against others who are either neutral or peaceful and is not justifiable. Defensive force repels offensive force and is a justifiable means.
Presently the legal and "justice system" doesn't really allow anybody other than Police to "police", unfortunately that kind of monopoly on force, is the source of the problem. Police routinely use offensive force, that's how they get paid, on an involuntary customer basis. so asking them to then eliminate or lessen offensive force (actual criminality) is self contradictory.
Centralized force based in an involuntary and contradictory means (see the first sentence above) can never solve the problems people assign it to solve, since it relies on the thing it alleges to be organized to prevent for funding. A giant illogical contradiction.
In other words, fixing the present Policing model, with a tweek here or there is an impossibility, since it is based in an INVERSION of justice from the beginning.
If the sentences above are true, (they are) then it is obvious what the solutions are. End the present Policing model and replace it with something that isn't a logical impossibility.