there is a satirical play, called "Goethe im Examen" (Goethe in exams) by Egon Friedell and Alfred Polgar, where Goethe has to answer questions about his life and fails miserably. One of the questions he is asked, is: what Goethes main achievement is and he answers "Farwelehr" (theory of colors) which, of course, is not the right answer, at least not for the professors. it tells us much about how he was perceived by literature professors but he himself might not have had the same perception of himself. unfortunately this play is only on the German WP:
https://de.wikipedia.org/wiki/Goethe_im_Examen