Well Marx is pretty fuzzy when it comes to details. Lenin had to apply the theory to the real world.

So I guess that begs the question -- what other options for an economic system are there besides:

1) "free markets" / supply & demand / "capitalism" -- in other words individuals make their own decisions about producing and consuming.

vs.

2) some form of "centralized control" where decisions are made for individuals, "for their own good" of course. ;-)

I don't know that Marx ever had a satisfactory answer to this question.

(And yes I admit I get my Marx-Engles-Lenin-Trotsky mixed up sometimes.)