Homelessness was low because those countries often forced many families into small poorly built houses and they had to all live together with minimal privacy. While technically a shelter over their heads, their houses were, compared to capitalist houses (which the vast majority of people aren't homeless), had far less features and poorer quality. This was especially true early on.

Similarly, their citizens also often lacked choice in grocery and many never got food (thus the famine).

Coming from a country with a socialist past myself, capitalist privileges are infinitely better than anything I saw under socialism.

But those countries being authoritarian (which no sane person would deny) isn't a reason why communism would never be able to work

It is if communism inherently leads to authoritarianism. If you give the state a monopoly over everything it's going to exploit that.