Communism does not necessitate self-sufficiency, moreover, a switch to fully domestic production is detrimental to any economy. The reason modern economy is globalized is that it's simply more efficient, and capitalist economies are all about efficiency, as it allows to extract more value. At the same time, many past socialist economies were forced to only partner with other socialist economies, which limited their options and hurt their economy.
One of the key reasons communist classics called for a global revolution is to gain the critical mass of communism-aligned countries to minimize this effect and maximize globalization efforts. The communist endgame is one interconnected world without any nations to begin with, not to mention any protectionism.