I think that's an ineffective and inaccurate way of looking at things. It's not reflective of the reality of the situations where we've seen anarchist communities rise (and fall). The Ukrainian anarchists all got killed by the Soviet Union, but so did everyone else. They beat the hell out of the monarchists, capitalists, etc in the region and had a good chance at establishing a major anarchist force in the world but ultimately the Soviets betrayed and killed them all. Does the fact that the Soviets killed all the capitalists and monarchists, too, mean their philosophies are utopian? After all, they couldn't fight off the Soviets in the same way the anarchists couldn't. They were even less effective at doing so in a lot of ways.

Yeah, the governments of the world do tend to all murder any anarchists they can get their hands on but that's not an argument in favor of big state governments. That's not really an argument against anarchism, either. Really, it's an argument against big state governments. It's weird to me that it's held up so much as if it "disproves" anarchism or whatever.

That said, if you want examples of anarchist groups that have managed to survive let's talk about two:

The first is the Zapatistas. This is a small group in Mexico that has been at war with the United States government and Mexican government for decades now. If the US government wants you dead but can't kill you, i'd say that's a pretty good "immune response". There are not a lot of people who can actively fight the US government and survive and there have been many, many, many other leftist movements in Central and South America that the US government has killed in the forty years since the Zapatistas got their start.

The second one is Rojava, aka more properly: the Autonomous Administration of North and East Syria (AANES). They're a bit younger, only officially establishing their independence a little over a decade ago, but they're in some ways in an even more hostile part of the world. They're a larger organization than the Zapatistas, too. It's unclear what the future holds for them, but then again that's ultimately true for all states. We'll have to wait and see.