Setting up an entire production chain, from raw resources to end-products, on a local level?
Who said that? Nobody ever suggested that idea. It is a dumb idea, and arguing against it is a pure straw man because it's not a concept, not a goal, and neither a necessary condition or outcome of decentralized socialist economy. It's about as relevant as saying a specialized shoe company will never take off because you can't eat shoes, hence capitalism will never work.
Marx's socialism was always about pointing out how workers actually already run all the
existing systems of production, but they usually get much less remmuneration than a handful of rich "owners" who don't actually do anything to run things themselves. So it's all about changing the management of
existing systems, recognizing that it's actually workers who built everything in the first place. Rich people have just been very good at ensuring that most of the productive labor in most countries never get a cut of owning anything. Like in India you work 18 hour days, 6 days a week for 40 years and you just own a pair of shoes and a TV or something. That guy built the system but
his children don't get a cut of the profits.
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"Decentralized" means decentralizing management and ownership of existing, well-understood production processes, not redefining those production processes or changing the fundamentals of how resource flow works. So, it proposes some new ideas on management, but the basics of industrial production aren't constrained in any specific way. In other words, Marx does not provide prescriptive ideas about how factories should make things, just about how managers should be selected and how the profits should be divided up.
There's a thing called "trade". In Marx's ideas communes are NOT local town councils. It's definitely not anything related to the idea of local self-sufficiency. Total economic self-sufficiency doesn't come up as a concept, and it doesn't naturally flow from the other ideas. local self-sufficiency harks back to feudalism, which socialists were definitely against.
Marx's idea of communes is a lot closer to worker-owned corporations, and the corporations in an area then come together to agree on higher-level goals and settle disputes. You're still going to be seeing specialization, flow of resources, competition and cooperation within such a system. Since a single commune will be effectively the smallest-grained unit of production, and autonomous, they will still be specialized in the production of a single thing, because that is what creates the most productivity. And just by natural law the most productive communes will grow, the unproductive ones will copy what the productive ones do or disappear. They will still be reliant on trade with other communes to provide all the things they need, and these communes don't have to be in the same region.
Many of the common criticisms against such a system can be shown to fallacious, and not based in any rational assessment of the scenario itself. For example since there is no central wage fixing in this scenario, the common argument that it would make people lazy because you get the same wage no matter what can be shown to be groundless. In fact, decentralized communism is more linear in it's relationship between productivity and profits than capitalism is (which tries to pay you a minimum wage regardless of how productive you are).