It's not the only thing to do, it's one of several things to do. Defunding reduces their access to weaponry and equipment and hinders recruiting. It's a big step toward abolition.

We live under Capitalism---let's use that to our advantage. Less money begets less power.

It's like energy in physics. You can worry about all the (perhaps more fundamental) mechanical, chemical, etc. interactions, or you can trust the conservation of energy and not fret over the details.

The abstraction works pretty well. Use it.