Aristotle was not against "capitalism" in the sense of the production, use, storage and exchange of CAPITAL GOODS [food, clothing, shelter, healthy water supplies etc.] which are necessary for life and are also what he called "natural goods" or goods of nature. But he was against what he called "artificial finance" and the unlimited acquisition of coined money. He considered that sort of "capitalism" to be a perversion of the desire for a limited amount of natural necessities, otherwise known as capital goods [food clothing shelter]. Quote
But strictly speaking, as I have already said, the means of life must be provided beforehand by nature; for the business of nature is to furnish food to that which is born, and the food of the offspring is always what remains over of that from which it is produced. Wherefore the art of getting wealth out of fruits and animals is always natural.
There are two sorts of wealth-getting, as I have said; one is part of household management [oiko nomia; Household laws = "economics" in English KB], the other is retail trade; the former is necessary and honourable, while that which consists in exchange is JUSTLY CENSURED; for it is UNNATURAL and a mode by which men GAIN from one another. The most hated sort [of men gaining from one another by exchange KB], and with the greatest reason, is USURY [i.e. lending money at interest in order to profit from loaning money KB], which makes gain out of MONEY ITSELF and not from the natural object [i.e. capital goods] of it For money was intended to be used in exchange [of capital goods KB], but not to increase at interest. And this term interest which means the birth of money from money, is applied to the breeding of money because the offspring [money KB] resembles the parent [money KB]. Wherefore of all modes of getting wealth this [usury; banking; exchanging means of exchange for profit] is the most unnatural. [Aristotle THE POLITICS, BK I, Ch. 10; 1258a line 33 to 1258b line 8].
So Aristotle is in favor of "natural capitalism" and opposed to "artificial capitalism" where money and the acquisition thereof gets confused with "natural goods" which keep body and soul together or the heads on one's shoulders. [Capital punishment = the removing of one's head by the state].
As to those who wrote about "capitalism" being either a "concept" or a "word" from the 19th century, they are confusing the age of "laissez faire capitalism", as coined by Adam Smith, with the distinctions made by Aristotle between natural capital goods and artificial goods (e.g. money).
The age of "laissez faire capitalism" (1813 - 1914), first mentioned by Adam Smith, came about as a consequence of the loss of British control and government over its "colonies" and the relative lack of governmental control/taxes over former colonialists, who then were left relatively free to invest the majority of their own time, energy and physical money in wealth producing/getting enterprizes --- relatively unhindered by "governors" or "governments".
What we call "capitalism" today, Aristotle would call unnatural or perverted artificial finance. He would also call "income tax" the reintroduction of universal slavery on a part-time basis and entirely INCOMMENSURATE with either natural capitalism or even artificial capitalism.
BUT your question could actually be about Plato's Communism vs. Aristotle's version of natural capitalism. Aristotle was definitely against the communism of Plato's Republic and definitely for "natural capitalism".