in the Critique of the Gotha Programme, marx attacks the idea that a society's distribution of goods can be justified by applying an equal standard of labour contribution to everybody. he points out that individuals have different physical and intellectual capacities, different circumstances, and different needs. treating everyone as an abstractly equal worker doesn't make those differences disappear. the famous formulation of "from each according to his ability, to each according to his needs" explicitly states "to his ability" and "to his needs" for this specific reason. he did not fail to account for the fact that different people have different needs, that was own critique of the contemporary social democrats.