This is more a question about economic histography, than economic history. The way that economic historians think about economic history has changed considerably in the period since WWII.  

The term "capitalism" was first used in the 19th century, as a label for the existing economic system in the UK and other similar countries.  This was a time when historians and economists talked about "feudualism" as a distinct system of economic organsiation that had covered much of Europe in medieval times. Karl Marx used the term "feudualism" extensively, and contrasted it with capitalism, viewing the two as having very distinct economic systems, with capitalism having replaced feudalism in a revolution where the bourgeois displaced the aristocracy. Marx's intellectual influence has been huge, and many writings in the 20th century, and even now, draw on this conception of there being something distinct about the economic system of the UK of the 18th-20th centuries, compared to earlier times.

 In 1944, this idea got another boost amongst intellectuals when the economic historian Karl Polyanki published his book The Great Transformation, which argued that the market society, in the sense of an economic system guided chiefly by profit-seeking behaviour, and market prices, was something fairly new, developed in England in the 18th/19th centuries and spread from there. Polyani did not deny that there were markets before then, it would be hard to do so, given that they show up as familiar references in the New Testament (e.g. the Parable of The Talents, and Parable of the Workers in the Vineyard), instead he argued that markets were relatively rare and that people's economic activity was guided as much by social custom and norms as by gains. 

However modern historiography, drawing on research carried out since then, has a very different view now of historical economic organisation. Generally, a lot more complex one that emphases variation between different places and variation in organisation at the same places at different times. In the case of England, the medieval economy is now regarded as highly market-based and accounts of the Industrial Revolution talk more about a gradual change. To quote the economic historian Gregory Clark:

The more we learn about medieval England, the more careful and reflective the scholarship gets, the more prosaic does medieval economic life seem. The story of the medieval economy in some ways seems to be that there is no story.

Back in the bad old days, when the scholarship was less careful, the medieval economy was mysterious and exciting. Marxists, neo-Malthusians, Chayanovians, and other exotics debated vigorously their pet theories of a pre-capitalist economic world in a wild speculative romp. But little by little, as the archives have been systematically explored, and the hypotheses subject to more rigorous examination, medieval economic historians have been retreating from their exotic Eden back to a mundane world alarmingly like our own.

Polyani's view of ancient economies has also been pushed back on based on more recent discoveries. 

Going back even further in time, the Hekanakhte Papers are a surviving record of Ancient Egyptian economic management from 20th century BCE, so over 4000 years ago. These papers are letters that a landholder and minor priest, Hekanankhte, wrote on a variety of matters, including instructions to the agent managing his land. He discusses grain and cloth sales, renting lands, debts, and the wages to be paid to various servants (apparently in terms of barley). It's not clear whether or not there was coins at this time but Hekanankhte clearly could convert values between different crops or crops versus cloths, which meets a [technical definition of money](https://link.springer.com/referenceworkentry/10.1057/978-1-349-95121-5_2742-1 at least). (Note I am not an Egyptian expert, am about a zillion miles from reading Egyptian hieroglyphs, and am totally relying on secondary literature here). One can argue about how representative Hekanankhte was, but it seems fairly clear that people have been operating in markets for millennia. (This is not to say that Ancient Egypt was a solely market economy, there is other evidence of government involvement, but then the 18th century British government wasn't purely hands off either.) 

Similar evidence has been found for other economies around the world and through time. Markets are, if not everywhere, at least highly common. The economic historian Deirdre McCloskey has criticised Karl Polyani for making an error symmetrical to the one you describe those libertarians discussed on r/badhistory - he assumes that any sign of government interference means the economy isn't a market economy, McCloskey argues that what should matter is the degree.

Nor is there clearly a trend to greater use of markets over time, things that were widely and openly sold in the past (e.g. military commissions, Anglican ministries, even people) are now illegal to sell, and many countries have extensive government provision of things like education, sewage and healthcare. This is not to say that there definitely has been a trend away from markets, either, just that it's complicated. 

There have also been a number of developments in economic theory and economic history that are hard to fit into a single-focus model where the main thing that matters is the reach of markets, such as the links between long-term economic outcomes and measures of social trust or that between short-term economic outcomes and the money supply. 

Therefore, economic histography, and economists in general, have generally moved away from the concept of "capitalism" as a useful label (it does show up a bit, mainly in the context of the 19th and 20th centuries as the alternative to "socialism", while the term "socialist" is also contested at least there's a bunch of countries whose leaders were so committed to socialism that they put it in said countries' official names). Instead the discussion is much more multi-factorial, and relative, most obvious in the indices of economic freedom produced by the Canadian Fraser Institute and the USA's Heritage Foundation.

 (Note that both institutions are ideological free-market think tanks, not neutral observers, who arguably have some incentives to rate the USA a bit on the low side as part of a fund raising scheme, also their indices have data limitations, e.g. very poor countries can't raise as much tax as a % of GDP as richer countries before the general population would start starving to death, I link to them not because I endorse these indices uncritically but to give an idea of an alternative classification system can look.)

Not surprisingly, this complex view has also overturned the idea of economies progressing from one stage to another. 

Personally I've not run into any academic source in the past 40 years who has looked at the range of findings from economic history and histography that I've mentioned here and still argued that the term "capitalism" is useful, outside fairly narrow contexts. 

tl,dr Economic histography since WWII has overturned the idea of "capitalism" and "pre-capitalism" as useful ideas. 

Sources

McCloskey, D,  Hejeebu, S,*The Reproving of Karl Polanyi* - pdf" Critical Review 13 (Summer 1999): 285-314.

Ezzamel, Mahmoud. 2002. Accounting for Private Estates and the Household in the Twentieth-Century BC Middle Kingdom, Ancient Egypt. Abacus 38 (2): 235. doi:10.1111/1467-6281.00107.

EH.net reviews of books about the economy in ancient mediterrean states, http://eh.net/?s=ancient+egypt