I used to wonder why systems analysis isn't taught

The last few months have made it extremely obvious why it isn't taught.

Stocks, flows, feedbacks, constraints.  The stuff that happens in the short term—the general operation of the system stuff—is the feedback.  In severe oversimplification, the stronger feedback wins.

In these terms, when you advocate for defunding the police, you're talking nonsense unless and until you're taking three things into account.

First thing is that the police absolutely will open fire in preference to submitting to civil authority.  They've been threatening just that for decades and they've nigh-certainly done that already even to the powerful.  (It's absolutely certainly when considering the not-powerful.)

Second thing is that, by defunding the police, you're attacking the enforcement arm of white supremacy.  Note what happens to notionally sovereign politicians who attempt to oppose the resource extraction arm of white supremacy; the same response is going to happen if you successfully defund the enforcement arm.  (That is, you get a coup and the political process is replaced and reverses the defunding action.  The Mammonite preferred outcome, private security forces, is at least not unlikely as a long-term outcome.)

Third thing is that white supremacy is an economic system.  It starts as a legitimisation ploy for looting; if you are easily sunburned, you are inherently morally superior and can take anything you have the strength to take from anybody who isn't easily sunburned.  This turns into a "hey, wait, let's steal abstractions like sovereignty and economy"; you get colonialism.  Somewhere around 1970, out of material stuff to steal but completely unwilling to accept fundamental structural change to the economy, the great and good decided that the purpose of the economy was not to safeguard wealth but to guarantee wealth; the Mammonite faction gets political ascendancy, and the idea that you don't get subjected to systemic looting if easily sunburned goes away.  The stack of axioms that permit billionaires, treating labour as a cost to be minimised, or the argument that being rich should free you from paying taxes are, in effect, the Mammonite heresy of white supremacy.  (Classical white supremacy sees the common interests of the ruling class as including long term social stability because if you don't have stability you have change.  If you're already on top of the heap, all change is bad, because you're overwhelmingly likely to be worse off, you have nowhere to go that isn't worse off than your current position.  The heretics aren't zero-sum conservatives; they're negative-sum death cultists.  The point is not to preserve existing relative eminence, but to guarantee eminence by reducing everyone else to misery.  (misery limits your scope of political opposition to something certainly ineffective.  Very important when you're expecting people to submit to being part of the mass extinction.))

So that's what we've got.

What's the least sufficient thing to have stronger feedback?

As a Canadian example, to abolish the RCMP, raze RCMP headquarters in Ottawa, and convert the underlying land to indigenous sovereignty, complete with sufficient funds to remediate it into something other than a hole in the ground.  If you don't have the political power to do that in such a way that it sticks despite a dead-eyed kitten eater getting in with a majority government, you don't have enough political power to defund the police.

That's not going to happen as a single step.

All power is unitary.  If you want to reduce authoritarian white supremacy's functional power, you go after the thing that funds it; great personal wealth.  (It's a system for increasing retained loot!  It has never been anything else!)  That DOES NOT mean that you insist that people pay their taxes, have the tax authorities do hostile audits (richest first!) or that you start responding to obfuscated assets through forcible liquidation and permanent penury.  All that's doing is shifting the direction of hostility from the authoritarian system.  (The public sphere equivalent would be making rules that say there are no white cops or male judges for the next hundred years.  Emotionally satisfying but ineffective policy.)

The effective steps are producing economic alternatives; removing the limited liability of corporations ("I cannot be held responsible for the collateral damage of enriching the owners") and creating collective forms of land tenure and social organisation.  (Remember that the big problem with indigenous anything comes down to land tenure; from the viewpoint of the extractive wing of the authoritarian white supremacy, nothing is permitted to tell them they can't have that.  From the viewpoint of the Mammonite wing, nothing is permitted to reduce the cash flow.  Look at trends in land tenure since 1950 and you see "only corporate ownership is legitimate ownership" very clearly.)   You're after an economy that creates not only a "this is better" feedback but a "we don't need them" feedback.  Get it out of the context of control of the authoritarianism -- let the authoritarianism collapse for lack of economic participation -- and then you can start the audits.

So, sure, defund the police.  But the human economy has to be there, too, or it shan't stick.