Requiring evil to understand goodness is, in fact, asking for pain to understand what it's like to not suffer. Adam and Eve were aware of just how good the garden of Eden was even before they were banished. If enduring evil is the only way of truly knowing God, then the first couple could not have known God without having eaten the forbidden fruit. In that sense, hasn’t indulging in evil actually benefited mankind?
God is omniscient, omnipotent and omnipresent. As such, He is all-powerful and has the ability to destroy evil should He want to. But if God requires the assistance of his archenemy to help mankind be aware of His presence, how does that make Him omnipotent? Instead, it would show Satan having greater power than God as it would be only through him that human beings could know God.
This inconsistency shows that theodicies do not explain the reason that God allows evil to exist. If it did, then this paradox would not exist and neither would the debate.