Ultimately, there are just to many other characters who have a stronger case to being the champion of magic in the DC universe.
Doctor Fate is a god using a human body as a conduit and is repeatedly referred to as the most powerful magic wielder in the world.
Captain Marvel was imbued with the power of five gods by a magical wizard whose declared that Billy will take his place as the Earths mightiest mortal and is explicitly referred to as the champion of magic on multiple occasions.
Zatanna whose probably the most active and prolific superhero magic user.
And even Constantine whose basically magic Batman.