4e fixes the spellcaster problem by giving them the same sort of abilities had by every other class. It's a fix, albeit not the sort many people expected (which might have been reduce the power of spells and increases the defenses non-spellcasters had against them, for example).
For many players, the old style was a feature, not a bug. If the goal was to play Merlin, Gandalf or whatever, then the player at some point wanted to wield phenomenal cosmic power. For these players, 4e is entirely unsuited to their gaming goals because a wizard can do nothing that isn't fundamentally mundane. Sure, they can do damage, attack something other than AC, apply conditions, move the target, and move themselves and some of this impressive and perhaps can't be explained easily in mundane terms, but every other class can do all the same things and sometimes these things can't easily be explained in mundane terms either. While it creates a level playing field, it isn't paying much attention to simulating either fantasy source material or, as is probably more important in the case of your friend, the flavor of the play experience he's used to for the last 20 years or more.
I don't think this is a crossable gulf.