Marx didn't specify many details about how a communist society was meant to be run, but he did specify quite clearly how it was meant to be created. See the numbered list at the bottom of the Communist Manifesto:
https://www.marxists.org/archive/marx/works/1848/communist-m...
Observe that he prescribed:
1. Abolition of private property
4. Confiscation of property of all rebels and emigrants
5. Centralisation of all credit in the hands of the state
6. Centralisation of all communication and transport in the hands of the state
9. Forced mass population transfers out of cities into the countryside
How can anyone implement such drastic policies? Marx was under no illusions about this and spelled it out quite clearly, which is why the fact he's not perceived as being as evil as Hitler is an unfortunate stain on our society:
Of course, in the beginning, this cannot be effected except by means of despotic inroads ...
So he literally stated in his manifesto that creating a communist state would require despotism, or in more modern language, totalitarianism. That was just one of many calls Marx made for violent revolution rather than democratic means.
Given this starting point it's not a huge surprise the Soviets tried to implement a fully planned economy. Marx didn't specify that as an end state per se, but he specified very similar things as a means to get to communism. China still has a largely planned economy despite successfully whitewashing itself as "capitalist", hence all the stories about staggering piles of non-performing debt, zombie banks kept alive by government fiat (centralise all credit in the hands of the state), and massive overproduction of things like steel.
As for Poland in the late 80s, yes, by the end of the 20th century a lot of committed communists had realised how foolish they had been. But did they really understand the true root cause of the problems? Or did they mistakenly conclude the root cause was central planning? Sometimes when I look at the behaviour of the eastern European states I have to wonder.