I’m not sure which post @Objection@lemmy.ml is referring to, but in simple terms, markets are useful in that they stitch together and connect production. This is a progressive development on disparate, unconnected production, be it for necessities or for luxuries. However, once production is all stitched together, it’s easier to see the whole and plan it, by which point the progressive aspects of markets have outlived their usefulness.

What’s key, though, is control. Class struggle remains alive until it ends. In order to maintain socialist control, the large firms and key industries need to be dominated by a working class state. This way capitalists cannot leverage control over the means of production and turn it into political power, they are kept to secondary and highly competitive industries in a birdcage. They may fly as they see fit within those bounds, but the owner of the cage can shrink it as they see fit.

Capitalism’s historic role is in connecting humanity. In other words, in socializing production. The working class’s historic role is socializing distribution as well, moving from the chaos of markets to a scientific plan gradually after siezing political control.

Hope that helps!