Communism is supposed to be decentralized and democratic. I assume you mean the Soviet conception of communism was a traditional top-down rule from above. (It wasn't communism)
https://en.wikipedia.org/wiki/Kibbutz
I don't know if this count as "communist" but they are two type of collective egalitarian democratic organisations that have got some success.
Why would you think that a political or economical system needs to be globally scalable to be useful? Or that it would even be desirable?
It would be reasonable to believe that a family, a business or a city should not be governed in the same way a country or a planet is.
But a political system that scales globally is definitely desirable; an awful lot of human suffering is directly traceable to sub-optimal decisions made internationally because "those people" aren't "our people." There are big wins to be had for solving that problem.
https://en.wikipedia.org/wiki/Mondragon_Corporation
What is interesting is that once you look into it, it is structured similarly to some of the conglomerates (keiretsus) of Japan. Basically they have their own bank etc, in part because external banks were not interested in doing business with them.