Administration is not itself a class, and is necessary for any large-scale economy. Marxism opposes capitalism in theory and in practice. Management of industry is not the same as owning said industry. Marxism has never been about eliminating managament, because managers are not a class in and of themselves, but instead a section of the proletariat that perform necessary roles in coordinating production, distribution, and logistics.

Where did you get the idea that Marxists oppose administration from? It certainly isn't found within Marx and Engels' writings, without severe misunderstanding. Moreover, you're displaying black and white thinking in believing administration under socialism is the same as capitalist ownership outright.