You're assuming socialist/communist economies must, for some reason, be run exactly the same as capitalist economies. Of course if you're trying to mix both it will collapse.
The point of Marx isn't that we should create markets where the value is decided by the amount of labor. The point of Marx is that if Labor creates value, then Labor should be in charge. The problem being that Labor is hard, so the end goal cannot be to maximize Labor (or value), contrary to your implied way of thinking were the most value must be created.
If maximizing value is not the goal, then why should Marxism redefine value in a counter-intuitive way?
Btw, "Labor" cannot be in charge, outside the UK at least, because Labor is an abstract concept. In Marxist societies people are in charge that pretend to have the laborers best interest in their hearts. But as they "Some are more equal than others."
> If maximizing value is not the goal, then why should Marxism redefine value in a counter-intuitive way?
Because it's only an exchange value and doesn't take into account the myriad of things that also have value but are not a consequence of work ? And the goal of Marxism might not be to maximize exchange value ?
> In Marxist societies people are in charge that pretend to have the laborers best interest in their hearts
Hard disagree, looking at societies applying values evolved from Marxist theories I see people in charge of themselves. I think of the old Commune de Paris, of the Spanish Revolution, of the Rojava. You need to look further than the one example you have in mind.
The point of Marx isn't that we should create markets where the value is decided by the amount of labor. The point of Marx is that if Labor creates value, then Labor should be in charge. The problem being that Labor is hard, so the end goal cannot be to maximize Labor (or value), contrary to your implied way of thinking were the most value must be created.