You are correct. The fighter (and rogue, and to a lesser degree the barbarian) should NOT be mundane. They should be magical.
The fighter should never be "dude with a sword". The fighter should be "dude with supernatural ability who channels it into his sword". He should be born of the Gods, have dragon's blood in his veins or heir to the giant's legacy. He should breathe fire, sheath his weapon in energy, sprout wings and fly, and at 18th level have abilities that start "once per day, when you die..." The rogue should be walking through walls, disappearing Batman style during conversations, stealing hit points to provide him temp hp, or using supernatural aim to guarantee the next hit they make is a crit. The barbarian is riding this line already, lets push him over with rages that channel primal powers. There should be NO mundane subclasses and they should be looking at the bloodhunter and the monk for the level of supernatural ability all classes have bare minimum.
A cleric isn't a village priest. A rogue isn't a common pickpocket. A wizard isn't a local scribe. A fighter shouldn't be a town guard of infantryman. Mundanity is for NPCs.