First, the USSR and China under Mao were not communist and did not even claim to be communist. So you have to understand that many people who are advocating for communism do not even want to emulate the Soviet Union. They are talking about a fairly different system. In fact, communism is theoretically meant to be stateless, so it shouldn’t really have a government in the sense that we would understand, though there is some debate over exactly what this means.

But most people who have studied history recognize that the Soviet system of government did not work well and oversaw numerous crimes against humanity. Of course, the same can be said for many western governments. And it’s worth noting that it’s not very clear that capitalist governments have been particularly better at avoiding famines. Several examples have already been given in this thread.

In fact, since the discovery of modern agricultural techniques, the majority of famines have been caused not by environmental factors but by the deliberate and usually violent deprivation of people from land and food resources. Recognizing this fact, which is common to all types imperialist powers, whether western or eastern, allows us to see that the root cause is not the economic system but the political system. Specifically, the oppression and exploitation of one group of people by another which happened in the USSR and China and happens today and historically under US hegemony.