In a way, Magenta's job is not besting Bach. By the definition of Bach (a human being who changes the way we view and enjoy music), a non-human being cannot best Bach. Magenta's job is besting a much simpler, if equally challenging role - Max Martin, or the writers of "Let it Go".
As it turns out, this kind of music is already pretty formulaic. Much has been written on repetitive chord progressions being spammed across hundreds of famous singles. In a way, artists shouldn't fear the potential of these technologies besting them - they should thank them.
Freed now are artists from loading their albums with eye-rollingly generic lead singles that they immediately get sick of ("Stairway to Heaven", "Creep", "Smells Like Teen Spirit") because record labels know that's what will get the most radio play. You can just let the machine do those. Now, an artists' reputation is determined purely by his relative mettle against other human artists.