As for the discussion about the leaders in Civ VI, I think they are an essential part. Let's be honest: would Civ VI be the same game if you played against the Netherlands without Mama Tulip yelling at you for not sending trade routes, or playing against Brazil without Dom Satan getting on your nerve? Would Sumeria be better without Gilgabro (no, nevermind, this question doesn't serve my point).
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As for the all debate upon Venice vs. Italy, I think the big problem we have here is the more fundamental debate upon blobization versus factionization
On one hand, blobs are an affront to God: not only do they are a complete misrepresentation of what the civ historically was, but it also feels too gimmicky. We all agree here that we ought to prevent blobization.
On the other hand, do we really want a game where we ought to separate every blob into more honest and historically accurate factions? Germany would be forbidden then in favor of the HRE, Prussia, Austria ; Spain migfht be in need of being cut into Aragon and Castilla ; France would need to represent only the Ancien Régime or Post-revolutionary, but not both ; Greece would certainly never happen again, as well as any representation of Phoenicia and Carthage ; ... Factionalization is what gave us England+Scotland (while both being very british), but also Canada+USA+Australia (especially Canada+USA; even mechanically they do not make sense to be separated, both being two civs focusing on diplomacy and national parks).
Moreover, if we go the route of factionalization, if will mainly be done for European/Western factions. See how we're debating over Italy, or over the need for Austria while we already have the HRE represented by Barbarossa and Germany's UA. So if we go the route of factionalization, we will get England+Scotland+Ireland, three civilizations for two pesky islands, or three post-colonial british nations, and more.
As always, then, the virtue is in the middle. For the question for blobization versus factionization, the answer that we ought to ask before even having questions of representativity and historical accuracy is: would a blob of this culture could be well done and represent accurately most of the factions of this blob without making the mistake of representing only a small fraction of this blob, and does a fractionization of this blob would be different enough from one another culturally speaking to justify the fractionization?
Let's compare Civ V Celts and Civ VI Gauls to answer this question :
Civ V Celts had a UI quite specific to Ireland, a leader from Wales, a UU specific for the Picts, and a UA which would more represent the Western Celts than the Eastern one. Each element of the Celt toolkit is nitpicking elements from different subcultures without anything unifying other than a name -> Bad Blobization
Civ VI Gauls have, true, a specific UU (but, to be honest, UU are bound to be specific from a spacetime period), but the CUA directly refers to the birth of gauls and celts, the Oppida were quite common for all Gauls, and the Leader, while never leading all the Gauls, was one of the most unifying one -> Good Blobization
Same for Greece: it's a good blobization because both leaders aknwoledge the differences between differents sub-city-States, the CUA is quite representative of the interest pretty all city-States had for political philosophy, and the Acropolis were found often in most of greek city-States ; moreover, while being ofter at war, Greek city-States still considered to be part of the same culture themselves, differentiating themselves from the Barbarian outside who weren't allowed to take part in the Olympian games -> Good Blobization
On the other hand, we have English with a British leader, a British CUA, a British UU and a British UI, and Scotland with a British UU, British UI and British CUA -> Bad Fractionization
And on the final hand; Civ 6 Germany: CUA, the leader and the UI all redirect towards the HRE (were those three things were shared with the entirety of the HRE), while the UU is more modern and doesn't quite fit with the rest -> Semi-good/semi-bad blobization
So, now that we analyzed it, what is preferable for Renaissance Italy: blobization or fractionization?
My personal opinion is blobization, and this is why:
What interest us in Renaissance Italy is the cunning politics between the city-States, the wonderful flourishment of arts and culture, and the interest of most influential families in trade. Can those three characteristics represent Florence, Venice, Genoa, Milano, Bologna, the Papal States? Of course! All the most influential city-States followed the same pattern: making trade, sending spies, do some patronage for artists, and so on. Therefore, a blobization of Italian city-States would make sense. Give it a unique Theater Square (it would fit because all Italian city-States dabbled in culture and patroned artists to some extent), a CUA around trade and money (it would fit because all Italian city-States were major traders and financial geniuses), a Leader with a diplomatic/city-States/spies bonus (while it would technically represent only one city-States, would still it would work because all city-States had leaders masters of diplomacy, and even Vittore-Emmanuel II would fit then with his Risorgimento), and while I do not have any warfare history literacy, don't tell me that there isn't any specific unit from the Italian peninsula that could fit. Therefore you could gave to a Renaissance Italy blob specific CUA, LUA, UU and UI that screams italian without making the mistakes of representing only a fraction or a specific faction or this blob.
TL;DR: a blob of Renaissance Italy would make sense because you can make an Italian civ with abilities and uniques that would scream Italian without being tied to a specific faction of Italy.
