@Ridgerunner capitalism is not synonymous with trade and barter in currency.
Capitalism is about competitive production for the market, in the context of a comprehensive economic-social system in which "land” and “labour” (aka human lives and the environment as a whole), are regarded as commodities that can be bought and sold.
And that foundational understanding of human labour, it’s commodification, is described by the church as a “reversal” of God’s divine plan in the Book of Genesis: the idea, fundamental to capitalism, that work is merely an exchange of money for labour, which the church opposes.
As Pope St. John Paul II explains:
In all cases of this sort, there is a reversal of the order laid down from the beginning by the words of the Book of Genesis: man is treated as an instrument of production, whereas he–alone, independent of the work he does–ought to be treated as the effective subject of work and its true maker and creator.
Precisely this reversal of order should rightly be called “capitalism”…
Everybody knows that capitalism has a definite historical meaning as a system, an economic and social system, opposed to “socialism” or “communism.”…
It should be recognized that the error of early capitalism can be repeated wherever people are treated on the same level as the whole complex of the material means of production, as an instrument and not in accordance with the true dignity of their work
Laborem Exercens (“On Human Work”) , Pope John Paul II, 1981 #30.
In sum, with this encyclical JPII endorses labour over capital, asserts that work is not a commodity to be sold, castigates the maximization of profit, calls for worker solidarity through trade unions, a just family wage, health insurance and describes capitalism as a reversal of God’s divine plan in Genesis.
Medieval merchants got a profit through commerce, certainly, but by buying cheap in one locale and selling expensively in another,
however, they did
not organize production, nor did they depart from the feudal structure in which they operated with it’s self-sufficient peasants largely living off the commons, while their manorial lords provided military security and civil justice in return for a portion of the produce of the community they governed.
If you think that’s what capitalism is then I’d suggest you study it a bit more.