I am well aware of a spell casters numerous abilities (as I myself play an almost epic Lv Cleric) But as the fact stands that not all of them are useful at anytime, the end goal remains the same, to vanquish the enemy. (we're talking combat here) You have buff magic, fighters have much more health, also and desired magical effect that I should find to be useful, I can purchase. So to address your argument, yes it is true, that fighters are slightly less versatile when fighting unconventional enemies. But fighters do not need to hide, or flee.
As my DM once told me, there are 4 types of players in D and D
-- Those who say, I will hit you many times, and you can try to hit me once (dex fighters)
-- Those who say, hit me if you want, but I will hit you harder (Str fighters)
-- Those who say, try to hit me, my armor is to thick, and me DR is champ (tanks)
-- And then those who say, I'll hang back and attack from here/aid my allies (archers/spell casters)
They are wide categories but I felt that they would help solidify my point
(btw have you played a melee combatant before?)