Your claim about communism is false.
Which one? That it failed everywhere? That it killed a hundred million in the last century?
That East Germany's and North Korea's economies sucked compared to West Germany's and South Korea's?
All of your claims are misleading as well as the premise behind them. For the sake of others, I will explain why for the 586th time. You fail in assuming that if an economic system or mode of production is the successor of another earlier system, it must replace its predecessor immediately or within a certain arbitrary period of time (set by you of course). That's your first mistake. Asserting that since attempts to establish communism in the past at a national scale have ultimately failed, such attempts
WILL ALWAYS FAIL. That might be your wish, fantasy, or dream, but it's an illogical fallacy.
Your other error is in assuming that the reason that the USSR and other communist countries have failed economically, is only due to an endemic trait or flaw in communism. Well, that's not necessarily the case. You conveniently ignore and refuse to acknowledge the fact that those who are in power (i.e. namely the capitalists) as a result of an older economic and social order aren't going to allow a new system to be established if it poses a threat to their authority and control over resources. This socioeconomic class of elites we call "capitalists", will fight tooth and nail to stop the paying-consumer and general populace from having collective ownership over the means of production (i.e. the machinery, facilities/factories, raw materials, mining equipment, vehicles. etc), at a national, societal scale.
This capitalist "tooth and nail" struggle consists of communist countries being bombed, invaded, sanctioned, sabotaged, demonized. etc. You conveniently and disengeniously fail to factor that in to the equation pretending that the only reason that communists have failed in the past to establish a sustainable communist economy at a national scale is due to some inherent flaw in communism. Well no, not necessarily.
You pretend that the USSR failed, only because communism doesn't work. That's like throwing someone in the boxing ring with one hand tied behind his back and an eye patch covering one of his eyes, then you saying "see he can't fight". He sucks at boxing, see how he lost? Well maybe he doesn't really suck at boxing, perhaps you suck for tying one of his hands behind his back and blinding him in one eye. If you're in a position of immense power as the United States was and still is, then there's a lot you can do to undermine a smaller, developing nation's effort to successfully socialize and democratize its economy (i.e. adopt a socialist economy) and society.
The USSR and practically every country that identifies itself as having a Marxist socialist or communist economy will be targeted by the US capitalist empire and its crony allies around the world. That's the nature of the beast. For those of you who are reading this "friendly exchange of ideas" and would like to learn more about what really occurred in the USSR, watch the videos I'm going to embed below and read the informative PDF books I will attach to this post.
Another mistake that you're making is in assuming that capitalism and its original mercantile class, replaced chattel slavery and feudalism overnight. It didn't, it actually took centuries for the merchant classes to become the wealthy and powerful industrialists of the 1800s. They replaced the former royal aristocracy and nobles, with their capitalist-run, constitutional republicanism and plutocracy. Capitalist, entrepreneurial mercantilism began in the 1500s, with fleets of ships sailing to the new world and Asia, manned with employees (sailors, mercenaries). That's what led to the English civil war with Oliver Cromwell, establishing the British parliament. In other words, capitalism and its close relative, Republicanism, took centuries to replace slavery and feudalism, the kings and queens.
The process of replacing the older monarchal systems with all of its aristocratic lords and nobles, with a new and better constitutional-based Republican, capitalist-run plutocracy, granting people more freedoms and rights, took centuries.
So why do you expect or demand communism defeat and replace capitalism in one decisive victory and swoop of the sword, to prove its validity? Really? No mistakes, no defeats, no falling down and getting back up, no process of learning from one's mistakes in order to improve future outcomes, no no no. If communism is going to be the successor of capitalism it has to do it
PERFECTLY ASAP, RIGHT NOW! Every rational mind asks:
"WHY?"
Marx wrote that material conditions determine if socialism and later communism can be effectively established. The merchants didn't become powerful industrialists until technology allowed them to industrialize. Communism likewise will not successfully establish itself in a world of capitalist powers, that will move the earth and heaven to stop it until technology
(material conditions) permits it to exist and flourish. Until it becomes obvious, self-evident, and necessary due to material conditions, communism at a national scale, will not exist.
Now I ask you again. What is your capitalist solution to the widely recognized and forecasted soon-to-be crisis, of employers replacing their employees with advanced 21st-century automation technology? How will capitalists capitalize on their products, when a significant % or even all of their products and services are being produced, stored, and delivered by robots, artificial intelligence, automated systems, self-driving autonomous vehicles, and super-computers? etc
Do you have at least a general idea of how capitalism can solve that "problem"? Because this so-called "problem" of technology making production incredibly efficient and automated, is for us communists, the birth of communism. It's the death of capitalism and the birth of a new era of communism. You know that, that's why you refuse to answer the question. You're dumbfounded, bewildered.
For the genuine truth seekers:
Some PDF books you can read:
drive.google.com
drive.google.com
drive.google.com