Look, I have been highly critical of the pictures posted as what should be represented by the Warlord class for a reason. Warlord was a terrible name for the class because, yes, any person of any class in charge of a savage army is likely to be called a "Warlord".
Anyone can steal. Anyone can kill for money. Anyone can lead pious folk in prayer. Anyone can learn to play an instrument or tell stories. Anyone can hang out in the woods. Anyone can Fight. Anyone fight for the cause of a deity. Anyone can follow an ascetic lifestyle.
By your logic, the only legitimate class is Wizard.
I think you will find that there are a LOT of D&D players who think that "the only legitimate class is Wizard".
And that IS at the heart of a LOT of the problems we have with building up any class which isn't an arcane spell caster.
It doesn't help that the earliest D&D campaigns run by the original authors were virtually all-magic-user affairs.
In any case, regardless of the name, anyone actually denying the real effect of small unit leaders in combat situations (even with trained and experienced combat troops) is ignoring the facts of the modern world and history:
Further the non-magical combat leader is a common trope in fantasy novels, television and film which more than deserves to be realised fully as a class in D&D Next.
It seems like realism is only relevant or desireable when it can be used to take things away from martial classes. There is a lot of deep-seated prejudice out there.