Even if state capitalism best describes Soviet society, and this still seems most reasonable, the Soviet Union is, in a sense, a new type of social formation. This means there is a lot of theoretical work to be done, and we can’t wait for someone else to do it for us. But we cannot stop struggling against Soviet expansion until we figure everything out. Soviet expansion itself confirms the assessment that the USSR is a class and exploitative society which the Soviet people must overthrow.

https://www.marxists.org/history/erol/ncm-7/cpml-ussr.htm

Here is some light reading for toh of the different theories of the USSR. The workers did not directly own the means of production therefore this is a state capitalist society from a purely economic stand point. The worker co-ops of today where workers directly own the means of production not through a form of state apparatus is what Marx ideal vision of socialism was.