100%.The only insult to football is your comment.
He may not be the greatest but there is a lot of people out there that think he is and I guarantee they know more about football than you and I
He went to a bottom of the table team in the Seria A, which was the strongest League back then, and turned Napoli into the best team in the competition as well as in Europe.
No one has ever accomplished this before and no one will again. And keep in mind he did this with so much instability off the field, it's just remarkable.
To doubt that he is not one of the all time greats is laughable.