Anarchy is basically the idea that government is evil, initiation of force is evil, taxation is evil, and we should all live in voluntary relations all the time with no laws and no institutionalized systems of justice or police or military because those are, like, oppressive, er something.
The problem with this is obviously that each of those claims is bullshit. So anarchy is stupid.
More specifically, on the issue of the initiation of force: sometimes you have to initiate force. And sometimes you need to initiate force in response or anticipation to something other than immediate physical self-defense. That is just the way it is.
If your country needs a highway system then you may need to initiate some force to get that put in place. A highway system is a value, and if you rely on insurance and voluntary contributions and donated labor time then you’re not going to get the fucking highway system built, at least not for another 50 years. This same type of example can work with a thousand other examples too. It is simply the case not only for a society but also for an individual such as you and I that at times the initiation of force is “proper” or “ethical” even if our immediate safety and life is not being threatened. This fact owes itself to how there are much more, much more important, and much subtler values at play than merely our immediate physical safety and survival.
If something is of value either to you personally or to a large group, or to the largest ‘group’ of all (a society) then some initiation of force is justified in furthering that value. Therefore the Ayn Randian view that initiation of the use of force is always wrong and that the government’s monopoly on the legal initiation of the use of force is always wrong, is actually wrong. It is wrong not because it is wrong per se, but because of the radical narrowness of the sphere of its concern when it comes to which values are justifying for the initiation of the use of force.
Furthermore, every being and every living being in particular is always using small initiations of force on each other, either implicitly or explicitly, grossly or subtly. It is not only necessary to do so, it is simply what it means to exist. One example of a small initiation of force is socialization as such, interacting with each other in social environments and relationships. The initiation of force is so encoded into what we are and into our systems of sociality and interaction that we do not even notice it anymore, most of the time.
So a theory like anarchy is basically deeply ignorant of reality, of the way things really are. And any theory that is ignorant like that is simply going to fail time and time again. Also, if an anarchy did actually exist it would be a race to see how quickly it could either devolve into mafia rule and mob gang violence versus be taken over by a neighboring non-anarchic country that actually has… a functional military and industrial technological infrastructure for producing advanced weapons.