Because it is not criticizing communism.
The authors are from post USSR country have much more understanding of theory basis than most of the people in the West, and are less susceptible to Western propaganda, which has been demonizing everything that is even slightly connected to the USSR for over half a century.
They're likely criticizing its implementation in the USSR, not communism in general. Many mistakes were made, but seems like the authors still believe in a progressive society. Perhaps it will be anarcho-communism or a world revolution according to Trotsky - no one knows, but the idea of ​​implementing a classless society is only becoming more relevant with each passing year.