As I note above, there are success stories with NGOs. The Zapatistas are still active and going strong. Also the Black Panthers in the US before they were massacred in an FBI operation.

When a society is annexed or wiped out, it can't really be said to be fault of the governing system that it failed.

I say "probably" because we don't know - nobody has ever tried communism yet.

Well, that depend on your definition of try. The common soviet revolutionaries were not fighting and dying to put Stallin in charge, or to enact purges and gulags. But revolutions are always tricky. We can't tell if the problem is communism or just a revolution going wrong.

But we have a branch of mathematics called Game Theory that is designed to model these situations in theory and it's very difficult to design stable communism even just in theory. Partially just because eliminating the owning class puts all that power into the hands of the political class. Partially because state is not pushed to run the economy properly when there is no competition to compare to. And partially just because there is no practical data, unlike for capitalism.

Regardless, between the risks and costs of a revolution, the uncertainties of entirely untested system and theoretical issue with communism, I find it very much preferable to work on improving social democracies, that we see working in Europe instead of risking it all on communism.

Though I don't know if USA is salvageable without a revolution anyway :/