Civ VII is going with the 'classic' image of the Hoplite in bronze 'muscled' cuirass, Corinthian enclosed helmet, metal greaves and Aspis round shield. As it happens, that was also the earliest image of the Hoplite, whose panoply and equipment changed dramatically over the next 350 years or so.
First to go, as near as we can tell from the evidence, was the bronze cuirass, which frankly wasn't that good as protection: sheet bronze thick enough to actually stop a thrust from a heavy spear was both heavy and dangerously hot in a Greek summer sun. At that time or right afterwards the helmet began to 'open up' to give better vision and hearing to the wearer. Then the bronze greaves were replaced by leather protection or none at all.
By the beginning of the Macedonian War that largely ended Greece as a separate set of states, the 'Hoplite' might not even be carrying his distinctive big round shield - versions of the Theuros, or elongated oval shield borrowed from the Thracians to the north were frequently substituted, the torso was protected by a linen or canvas armor (the linothorax, which could be up to 5 - 7 layers of canvas, leather or stiffened linen thick), and the only metal armor left was an open-faced helmet of the Phrygian or similar style (which, in fact, was sometimes replaced by a cap of felt, leather or wool: if heavily padded it could stop a blow from a club or mace as well as any metal helmet, and was a lot more comfortable in that Greek summer). In fact, except for generally smaller round shields and the pike as a primary weapon, the Greek hoplite was indistinguishable from Phillip's and Alexander's Pezhetairoi Macedonian infantrymen.
BUT making the in-game Hoplite indistinguishable from a potential adversary's primary infantry would be very confusing to almost every gamer out there except those few of us that got stuck with a degree in Classics, so the game rightly chose to show the definitive Hoplite even though in reality he only existed for a century or so - in Civ VII, he's likely to be around a lot longer . . .
It's the traditional Firaxian look of the Hoplite, and personally I like that they keep sticking with it, since it's my favourite. Portraying a unit during its heyday when it was dreaded on the battlefield is the correct way.
*During its prime, the hoplite wore the bell cuirass (Archaic era and early Classical), the muscle cuirass (Classical and early Hellenistic eras), the linothorax (Classical and early Hellenistic eras) and a bare exomis (Classical and early Hellenistic eras) while carrying Boeotian (Archaic era) or Argive shields (Classical and early Hellenistic eras). Firaxis correctly chose the muscle cuirass that surpasses the others in beauty. The linothorax with metal plates, scales or bare linen (Humankind went with a linothorax, and I wasn't a fan) has possibly non-Greek origins and was used by other civilizations too (Egyptians, Assyrians, Persians, Carthaginians, Etruscans), a testament to that is the armour's use by the Immortal in the game. The bell cuirass could have been used instead of the muscle cuirass, but the muscle cuirass is the evolved elaborate version of the bell cuirass. The exomis was popular during the Peloponnesian War where mobility was key, but the Slingers and Archers wear it in-game already (rightly so). I have to say here, that the muscle cuirass never disappeared completely after the Peloponnesian War, and its use rose again during the Theban Hegemony for reasons that can only be speculated. For the shield the Boeotian could have been chosen instead of the hoplon, or even a combination of both but not only the hoplon is more recognizable to the wider public who immediately associates it with the hoplite, but also the Purabettarah and Immortal units have wicker Boeotian-looking shields, so the Boeotian shield was omitted.
If the Hoplite had been portrayed during its final days of the 2nd century BC (having evolved by then to the Thureophoroi and Thorakitai) wearing either a chitoniskos or a combination of chitoniskos and mail armour while carrying a thureos which by the way was gradually adopted after the Gallic Invasion of Greece, then the unit would have looked identical to some other non-unique units in the game. Roman units (horseman and standard-bearer) have been spotted with lorica hamata, and the thureos is carried by Independent Celtic units as well as Roman Tier 1 Warriors. Some uniformity in the same unit isn't always a negative, either. If the unit had a combination of Illyrian, Corinthian, Chalcidian, Attic, and Pilos helmets (earlier hoplite), or a combination of Pilos, Phrygian, Thracian, and Konos helmets (later hoplite), it would have looked less impressive in my opinion. But still there is a lot of variety in Civilization VII, since the exquisite Corinthian helmets have three versions of crests! The tall archaic crest, the widely used common crest, and the rarer transverse crest.
Generally, If a unit changed slightly its armour, shields and helmets after gaining a tier, that would have shown some form of warfare evolution, which it would have been more historical, but we will let Firaxis reach that level of realism in a future iteration of the series. Even then, the Hoplite is one of those units that by having identical soldiers inside the same unit is always a positive because it appears to be made of a walking wall of men of bronze or automatons, the terrifying image the Greeks wanted to present to their enemies (other Greeks or barbarians).
*Note that I added the early Hellenistic era as the heyday of the hoplite because the hoplite phalanx was still strong and capable on the battlefield then (even if it wasn't dominant) and the infamous late classical and early hellenistic elite Hypaspists were essentially a hoplitic unit. See the use of hoplite phalanxes as either flank protection to the more immobile Macedonian phalanx or as a second line to guard the rear of the pike phalanx and to reinforce the phalangites in case a gap is created in the line and also observe how the confrontation at Chaeronea between the Macedonian phalanx and the Theban-Athenian phalanx wasn't so one-sided as some think (the battle was lost when the inexperienced Athenians broke the cohesion of their line in order to pursue the Macedonians which resulted in a complete rout aside from the Theban Sacred Band).