Since communism is idealistic and is supposed to be communal, collective, and cooperative, then it has to voluntary
You might be right that communism may be too idealistic for a national level.
But empathy is not just familial.
It is in our DNA, as humans came down from the trees and had no other means of survival than group support.
Much like Meerkats.
You see it historical novels like Herman Melville's "Typee".
Tribes of natives frequently took in shipwrecked European sailors without any familial connection.
{...
Typee: A Peep at Polynesian Life is the first book by American writer
Herman Melville, published in the early part of 1846, when Melville was 26 years old. Considered a classic in
travel and adventure literature, the narrative is based on the author's actual experiences on the island
Nuku Hiva in the South Pacific
Marquesas Islands in 1842, supplemented with imaginative reconstruction and research from other books. The title comes from the valley of
Taipivai, once known as Taipi.
[1] Typee was Melville's most popular work during his lifetime; it made him notorious as the "man who lived among the cannibals".
[2]
...}
en.wikipedia.org
The problems of the USSR are that Lenin/Stalin were capitalist dictators, and that centralization works against being able to be collective, cooperative, and communal.
If it is ever going to work, it has to be democratic and local.