Context
It is a common usage to call some right-wing movements in Western countries "reactionary". See Wikipedia:
In ideology, reactionism is a tradition in right-wing politics
Reactionary is defined by Wikipedia in this way:
In political science, a reactionary or a reactionist is a person who holds political views that favor a return to the status quo ante, the previous political state of society, which that person believes possessed positive characteristics absent from contemporary society.
Although it can be meant as an insult, sometimes it is not, and some right-wing figures even openly recognize themselves as "reactionary". This is the case of the French far-right political figure Éric Zemmour. He, as a self-described nostalgic reactionary, wants to go back to the old France (as of which French period, see the debates in comments). In general though, if I am not mistaken, European (reactionary) far-rights hold high the values of the pre-Enlightenment Europe, and want to come back to something near to this period, which sure enough they may fantasize.
Question
If some right-wing ideologies are reactionary, why are communism (Engels and Marx) and anarcho-communism (Bakunin, Proudhon, Kropotkin) not seen, by the general public and the media globally, as reactionary too, in their case extreme-reactionary?
Indeed, they want to go back to the hunter-gatherers kind of society. Marx and Engels coined the notion of "primitive-communism", a state which our society should go back to. The French anarcho-communist Pierre Clastres was also clear about it (Wikipedia):
Some, like Pierre Clastres, consider that the organization of certain traditional non-Western societies (such as the Guayaki) in different parts of the world (the Americas, Africa, Asia, Polynesia), which have lasted for millennia, are at least partly similar to anarcho-communism.
Hypothesis
I would say this is because they stress on something modern: communism emphasizes the preliminary phase of the people dictatorship, and anarcho-communism emphasizes the masses revolutionary struggles. Yet, this is not their project per se, only the means towards their project.