Good observation. Both Pope John Paul II and Pope Benedict XVI have recognized that a free-market system is much more conducive to authentic human development than a Marxist system. However, any socio-economic system is going to emphasize the human tendency to turn from God in particular ways.
A key difference between socialism and a market system is that the market system allows potential - including moral potential - to flourish for the benefit of others. The structure of socialism defeats even the best intentions; a society of smart, educated, holy people *still* cannot make socialism work.
Socialism does work — provided one makes certain allowances. A command economy works where resistance to command is zero. The military is an example: an army has its own cities (forts), its own schools, its own power, water, and sewerage utilities, its own airline, postal system, telecom networks, religious institutions, and justice system. Everyone in the army works for the same “company”, gets paid on the same day each month, and accepts the work assignments and duties issued them by their superiors. Job placement is accomplished from above, with people being placed into jobs on the basis of aptitude testing and the needs of the army rather than on personal desire. No one is free to quit his/her job at a whim. An army holds absolute control over the lives of its “citizens” (the individual soldiers) and can order any of them to perform dangerous or even potentially fatal tasks with no explanation or possibility of appeal. All work is done for the good of the collective, not the individual. No one is paid extra for longer hours or overtime; work proceeds until completed, however long a given task might take. Clothing is issued by the collective and is uniform, subject to frequnt inspections. Rations are provided by the collective and are plentiful and nutritious, if not always high in variety or flavor. Housing, transportation, and utilities are provided by the collective. Every member of the army works and produces according to his or her ability and receives in return the neccesities of life in accordance with his or her needs. An army (and to an even greater extent, a navy) is an example of socialism that works.
Other examples of succesful socialism exist (medieval monastaries, for example). The thing these institutions have in common is that in each the individual surrenders his own desires and ambitions to the will of the collective. If the individuals making up a given population do not object to living in a society structured like an army (or a monastery), then socialism can work for that society.
However, for those populations with a moral or cultural orientation opposed to collectivism, socialism cannot be made to function. In such a situation, socialism can only be imposed upon the population by force or fraud by a small elite of ideologues with the backing of a substantial portion of the army. This “revolutionary vanguard” then simply liquidates the smallholders, religious institutions, and hereditary landowners who possess capital (i.e. the means of production and other physical plant) and expropriates their holdings “on behalf of the proletariat”. Systems of administration form as the revolutionaries become the established authorities; tructures of control form as those with more charisma and/or ruthlessness “game” the system to accumulate power for themselves. Once one or more of these power players achieve the ability to liquidate their rivals, they overthrow the other members of the revolutionary vanguard and consolidate power in their own hands.
Capitalism has a similar pattern of progression, but that is beside the point. The point is that a command economy can be made to work so long as the people comprising a given population do not object to being under command.