Why do we consider plato as a philosopher?

He never argued anything, his works are just a dialogue between him and his teachers. It’s all like Socrates saying ‘philosophy good’ and Plato agreeing. Isn’t this just recording your teachers words and not philosophising. He never wrote his own philosophy and never argued for a view. His teacher also said all he knows is that he doesn’t know but plato wrote a lot. Isn’t this hypocritical?