Regarding anarchism, it's known that the reason it didn't work out in the attempts so far has not been an inherent flaw in the system, but external ingerence.
In the two cases that are most known to the public, i.e. anarchist Catalogna and Free territories of Ukraine, the reason why the revolution finally failed has been in both cases the intervention of Soviet Russia, that in the first case supported an antagonist faction (i.e. communists front in the Spanish Civil War) and in the second case it invaded the free territories.
I think in general it's not possible to disregard some ideologies on the basis that they never managed to be implemented, without looking at the context. In today's world, which is dominated by capital, it would be even harder to establish a non-capitalist society, but that doesn't mean that such a society would be less fair, free or just than capitalism.