You clearly are not familiar with the early debate of anarchism vs Marxism between Marx and Bakunin in the days of the First International, which resulted in a ban of anarchists in the Second International. Marxists advocate a dictatorship of the proletariat, while anarchists reject the premise entirely. Anarchists reject any kind of transition state on the road to socialism, and reject action from above as a whole.
Marxists believe the worker should own what they produce, whereas Kropotkinists and anarchists believe the products of labor, like labor itself are social and belong to the community as a whole.
Marxists and anarchists do share some things in common, both place emphasis on the maxim, "produce according to ability and give according to need", but it is incredibly ignorant to say anarchists are Marxists, ignoring the history and debate between the two ideologies.
