Let's assume one could even call those failures communism/socialism.[1] How long have we experimented with and developed socialism/communism? 100 years.
How long have we been trying to get democracy right? 2,500 years. With many starts, fits and failures, devolving into dictatorships many, many times. The self-proclaimed "greatest democracy in history" is guilty of genocide and slavery. Even today how much it is a democracy as opposed to an oligarchy/kleptocracy/plutocracy is questionable.
How about capitalism? 500-800 years. And in that time it has exploited, enslaved and murdered people, pillaged entire nations and continents[2], raped the environment, and poisoned every culture that has adopted it with the notion that "selfishness is a virtue".[3]
The only reason capitalism hasn't collapsed (yet) is because capitalists are smart enough to not do pure capitalism, knowing that it would lead quickly to revolution, and because the environment's revolt is just getting started.
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[1] “The west called [the Soviet Union] Socialism in order to defame Socialism by associating it with this miserable tyranny; the Soviet Union called it Socialism to benefit from the moral appeal that true Socialism had among large parts of the general world population.” ~ Chomsky
[2] The United States: "look how many people died in the Soviet Union's industrialization program!"
Socialists: "how did the United States industrialize again?
The United States: "look, you need to do a BIT of genocide and slavery to kick things off…" ~ Existential Comics
[3] One of the most beneficial things about immersing yourself in deep study of American history is that you get to a point where this country can no longer effectively lie to you about why it is the way it is. It disabuses you of the notion that the inequality we see is an accident. ~ Clint Smith