I'll take a stab at this, because I think I get where he's coming from.
Imagine you're on a team with Peyton Manning and you win the Superbowl every year. Winning the Superbowl is fun for everyone on the team, including the linebacker whose name no one ever remembers and even the guys who are riding the bench. They get Superbowl rings too. They're winners too, right?
Those of us who want a higher standard for fighters think that riding the bench, even at the Superbowl, is not an acceptable standard. Even being a random linebacker is not good enough.
If the wizard gets to be Peyton Manning, then the fighter ought to be William "the Refrigerator" Perry (a legendary linebacker). That's the standard (IMO) that the game ought to be aiming for.
I think this is the "don't worry about it" argument not the "it's better this way" argument.
"Don't worry about it, it's not really an issue because some people still have fun playing the Fighter even if the Wizard is a lot better".
It's not answering why the game is better if you always have to play the benchwarmer if you choose to play a fighter.