Balance. Why do we need it?

[Cosi]

It seems like you're trying to argue against that by saying that you could theoretically replicate Gandalf with spellcaster classes (though that would mean he had a LOT of abilities he never used) making him equivalent fluff to a D&D wizard DESPITE the setting in question specifically saying that he's an archangel and not a mortal at all.

Fluff isn't transitive. You have to argue about capabilities to get good results when doing comparisons. Gandalf's capabilities are on par with a Sorcerer that is roughly 6th level (probably a Stalwart Battle Sorcerer or something else that gets relatively few spells and some combat power). You can call him an angel, but that doesn't mean anything, because we're comparing different settings, where "angel" means different things. Gandalf is very clearly not a D&D angel, because he does not have all of the angel traits (found here).