Ethiopian tribesmen defeated a column of Italian tankettes, they turned them upside down and lit on fire, and when crew tried to get out speared them.
If the Maori uu bothers you, you can think that the unit represents a larger group of warriors than an armoured swordsmen.
My father served next to the Ethiopian Battalion in Korea, in which there were a number of men wearing a little blue and silver badge with the representation of a spear on it: meaning they had defended their country armed only with a spear: this was, in game terms, the Atomic Era!
And the Zulu Impis destroyed a British force of riflemen at Isandhlwana in 1879, but the next year at Ulundi Kraaal were massacred in their turn by British using the same kind of rifles but better tactics.
And when you say 'Roman Legion' you really should follow it with Which One? because the Legion at various times was armed with spears, long swords, short swords, body armor, no body armor, heavy javelins, and in virtually all cases was accompanied by up to its number or more of auxiliaries that could be anything from horse archers to mounted armored lancers to slingers, bowmen, light spearmen, light swordsmen, or javelin-throwing skirmishers.
ALL units in Civ are always Approximations, sometimes pretty close, sometimes wildy off compared to the historical antecedent. This approximation gets even worse once you get into the Modern Era and later: at Civ scale, any Modern Infantry unit also includes Mortars. Machine-guns, light Antitank Guns or Antitank Rocket Launchers, at the very least. IF (as it really should) the Civ Unit represents an Infantry Division, then it also includes antiaircraft guns, artillery, and probably tanks or self-propelled antitank/artillery pieces.
Which means that a large number of the late game units, like Machine-guns and Antitank Crews, are totally artificial as separate units - along with the Musketman, that hoary old Civ Staple.
So, us Historical types just have to Grit our teeth and keep playing...