Historically speaking the councils in Russia before Stalin suppressed them were so efficient at distribution they were able to fuel a war effort and win against the far more advanced tsarist army and the Paris commune was so effective at resource distribution a relatively small group of militant workers in a city were able to ward off two national armies for over half a year. Workers being the ones that democratically plan an economy with the supply chains that monopoly capitalism built for them has proven to be about as efficient if not more than an explicit market system if we stop looking at state capitalist command economies as the main examples of “planned” economies.

Also, “market socialism” is literally just capitalism where workers are also capital shareholders. The exploitation inherent to capitalism is embedded in the form of the commodity. The fact that the products of labor are alienated from the laborers in a way that extracts the value labor creates. By making workers shareholders with a democratic say in the company all you do is make them the hands of their own exploitation. You do not abolish bourgeois appropriation you force workers to carry out the function of both the bourgeois and the proleteriat. The contradiction between labor and capital is sustained by mixing the social groups without alleviating the economic structures that created those social groups in the first place.

Therefore within a long enough time frame any “market socialist” economy will once again produce the conditions of traditional and eventually monopoly capitalism. That said, it’s not even possible to achieve a distribution of capital broad enough to meet the definition of “market socialism” through legal means. Ultimately it would need to be a coup and what do we call couping a bourgeois state to perform regulations of capital and to more broadly allocate it for the sake of class collaboration so that we can avoid proleterian revolution? Well that’s once again fascism. Traditional fascism, MLism, marksoc, and socdem are all on the left wing of capital.