They’ve retconned much of the core to fit the “expanded”(i.e. watered down) definition of what a Paladin is in terms of the lore.
Its the same reason Trolls got Shamans and Priests instead of Witch Doctors.
If they would just add race specific spell animations and names (while keeping the mathematical algorithm on the back end the same), it would preserve class identity and lore instead of watering it down purely for the sake of game play balance.