You have to prove why they would run into the same problems, you're still making vague accusations of Anarcho-Primitivism being the same as Modern Anarchist structure. The lack of existing structure disproving the possible existence of said structure is the same argument Anti-Communists and Anti-Socialists make with regularity, and is similarly an incomplete argument.
I, again, am not an Anarchist, but your method of argumentation is fundamentally flawed and won't convince any Anarchist to join a Marxist movement. It lacks Materialism in its analysis and is of the same quality as generic Anti-Leftist argumentation. Instead, you should argue against concepts like ParEcon, Mutual Aid, and other Anarchist theory, without arguing against Primitive Communism.