1) We don’t actually know that there is only 1 infantry unit in the Modern era, do we?
2) As others have said, the unique units are not necessarily representative of the bulk of a civ’s armed forces. This isn’t Total War, and there is always some degree of abstraction to the units visualised. Real armies don’t have only ballista elephants, or berserkers, or donkey chariots either. I don’t think that anyone will reasonably infer that the Mexican revolutionary army was all-female based on a unit in a video game.
It always seems that any attempt to put even a single female unit in a historic strategy game receives a disproportionate amount of backlash against its historicity.
1. So far. Infantry class is now streamlined. and this is what I LOVE alot. Civ6 Unit class systems are very silly. and so many times full of pseudo units as follows
1.1 Musketeers; Before 1700 AD There rarely was a homogeneous brigade consisting entirely of musketeers, they were mostly combined units. with any other hand to hand soldiers like Spanish Tercio (and copycats conveniently called Pike and Shotte. Sure musketeers were trained to shoot in successive rolling volleys so to maintain a steady flow or lead rains upon enemy combatants (as long as their ammo lasts), but they weren't really good at hand to hand combats (not many were specially trained that way, forgot THAT French elite guards, they were cavalrymen or at least mounted infantry but not common footsloggers.)
Very few examples exists though, though these were temporary phenomenon
- Battle of Nagashino. where Oda Nobunaga made use of homogeneous Ashigaru arquebusiers to the great effect against Takeda Knights. he did so however by raising a palisade walls, and posted all of his arquebusiers behind that walls, and enemy cavalry charge is not a problem at all. though Warring States Era Armies of Japanese Warlords did use Pike and Shotte as well.
- Battle of Sarhu. Joseon musketeers held their ground against Manchu mighty cavalry with no pikemen support. This happened because mis-organizations of Ming-Joseon allies, that Ming sent Pikemen while Joseon sent musketeers and intended to unite somewhere. Ming pikemen however were out of sync.
- Janissary. (not confirmed, though they were actually multidiscipline infantrymen that trained to use every weaponry available, they were also actually combined arms infantry and might using either spears or pikes (in the same fashion as Macedonian Pezhetairoi, since Janissary pikemen or spearmen did carry roundshields)
- Russian Streltsy
1.2 Separate 'Rifle Infantry' and Machineguns. the two units were, at Civ scales. always organized as one. I'm saying that MGs are included as elemnts of modern Infantry (And even cavalry) from the very start, and even more so since 1915 AD onwards. there NEVER WAS a full regiment consisting of HMGs.
1.3 And same goes also to Antitank Infantry. there NEVER WAS, and NEVER WILL BE a homogeneous regiment of bazookamen or ATGMs.
OK Streamlining infantry class could render some units totally irrelevants (such as tanks!), but that's tactical problem that has to do with random seeds and not a simple 'Rock, Paper' Scissors'. Big scale TBS like CIV is fundamentally different to RTS.
2. Abotu unique units, some did indeed correctly replaces generic options.
- English Redcoats: These were indeed basic British Infantrymen for some 300 years, with weapons upgraded to match global standards at any given time. And sometimes were even leaders. Generally one of the best foot soldiers in the World of their times.
- Viking Longships: though this unit is 'shared' with anybody else around them. especially with North Europeans all share clinker ship building traditions.
- Arabian Mamelukes.
- Khmer Elephant Archers. This was based upon Angkor Wat bas reliefs. Elephants were primarly cavalry choices of Southeast Asia. and even so these were elite units, and only Noblemen can ride ones to battles (and conveniently, field commanders of all ranks). Before anyone in Southeast Asia. It didn't represent Khmers entire army though.
- Indonesian Djong (Later became Majpahiti Cetbang). though graphinally incorrects, these were their naval mights.
- Australian Diggers (Actual name is ANZAC Infantry).
- Greek Hoplites.
- Roman Legion.
- Japanese Samurai. No questions about it.
Others were not represented correctly, for various reasons
- Viking Berserkers; VERY FEW men within any viking warbans are indeed berserkers. There always be a better UU options, mine is Huskarls, also infantry but more numerous.
- French UUs. BOTH 'Musketeers' and 'Imperial Guards' represents a handful if French infantry forces, in fact these were elite guards, surely better than average joes. but does NOT represents the entirety of French Infantry Forces.
Better Alternatives: There were better alternatives to represents French Infatry being superior--Le Blanc. and this represents the entirety of Basic French Infanry forces of the Late Earlymodern and Industrial Era (under Civ7 rule, Age III)
If 'Fusilier' name is not taken as generic unit choices. it should be taken as French UU especially with French basic infantry are conveniently referred to as Fusiliers since 1700s onwards.
- Amercan Rough Riders (under Theodore Roosevelt). They were irregular cavalry, and just like Berserkers and French Imperial Guard, only ONE regiments existed.
Better Alternatives: Yellowlegs. This is a nickname of US Cavalry since trousers runners are yellow. US Cavalry was modelled after British Light Dragoons, which still even by the time of American Revolution - still performs mounted infantry action - dismount to fight on foot whenever ordered to, something no Dragoons or Carabiniers in Europe bother doing by then.). US Cavalry are alwys gunny, and in fact the first to use repeater firearms. (and 'the most modern', one that geared towareds future trends, and not the past traditions because they had no traditions of European Cavalry at all. No Lancers, No Cuirassiers ever raised by US Government, and no knight caste requirements because there's none in America.)
- Brazillian Minas Gerais. The WORST UU Ever, These were once the best Dreadnought Battleships built, though these were all imports from Great Britain. made with superior specifications than what Royal Navy's best ships did. Minas Geraise was unfortunately outclassed too soon by Superdreadnoughts of 1910s. Also Brazil's lack of sufficient industry and facilities to support Dreadnoughts prevented this Pride of Nations to join any wars. Even worse it was a site of mutinies.
This represented Latin American Dreadnought Races of the early 20th Century, quite a flash in the pan since no one in Latin America had a through understandings of Steam powered, Steel hull navy. Over reliance on Agricultural exports eventually ruined these navies considerably.
I can't really think of better Brazillian alternatives at all. the closest might be either Prachinhas, or LLL (Napoleonic era Light Infantry, trained in the same fashion as British 95th Rifles - Skirmishers capable of linear infantry tactics).
- Russian Cossacks. 'Cavalry' replacements is a pure fantasy. Russian Imperial Army organized Cossacks differently to anyone else. They were irregulars that worked side by side with generic cavalrymen including a simple Line Cavalry. and they NEVER replace generic choices AT ALL and in all classes. Even generic 'light cavalry' exists - Dragoons. and these were hardcore mounted infantry.
Better Alternatives:
A. Streltsy. Backbone of Tsardom of Muscovy military. Musketeers that also equipped with a bardiche (a kind of poleaxe), granting a good hand too hand factor. What they used against cavalry was Gulyay Gorod (Mobile Fortress), of all kind. the most advanced iterations could be conveniently imagined as being a 'transformer'.
B. Corps Volante: Russian dragoon that replaces cavalry, gains cavalry mobility but use Infantry attributes in combat.