At the time of the Republic's demise, the Venetian state granted the right to participate in the Major Council (or "Great Council" as you call it; the archaic Italian "Maggior Consiglio" can be translated either way) to every single of-age male member of dynasties listed in the Republic's "Golden Book." This means that at the time of the Republic's end, between two and three thousand people were eligible to sit in the council. The unwieldiness of the Republic's keystone political body is, fundamentally, the reason why the Venetian model of government hasn't been replicated since the Republic's end.

The answer to other parts of this question would instead depend on when, precisely, you are looking in the Republic's thousand-year history: the Venetian government changed significantly over time, typically (but not exclusively) in response to crisis. Sometimes the changed made by the Venetians helped them successfully manage the crisis, while other times they did not. Oftentimes, the Venetians scrapped by with doing just enough. With each new crisis different political factions emerged, while in time, old political factions subsided. Thus the factions in the Republic's early history (landowners pitted against merchants and navigators) were significantly different than those in the Republic's final days (Destitute aristocrats, pragmatic isolationists, a small cadre of proto-nationalists, and an even smaller group of local jacobins).

At its root, government as envisioned by the Venetians was not altogether different from that which developed in most of Medieval Italy: influential people came together to agree on a leader, whose main prerogatives were settling internal disputes (either in-person or by appointing judges), settling external disputes (again, either in-person or by appointing emissaries), and overseeing public works. As time went on, the Italian communities developed institutions to regulate their leadership, based on the senatorial-style city-centric government that had existed since the roman period. While many cities organized political representation around the economic roles in society, the Venetian government distinguished itself in insisting on mob-style acclamation of political leaders until fairly late, and subsequently making a rapid change to a system of hereditary representation. The Venetians were also uniquely immune to the inherent weakness of the Italian urban governments; while in time the governments of Italy were slowly overtaken by single dynasties building spheres of influence which would ossify into a half-dozen sovereign states, Venice's political history runs in the other direction: political power diluted itself in time.

The Venetians' leader, the "Doge," was for much of the Republic's history the central figure in government. The word itself is a local variant of the latin "Doux," a title typically denoting a military leader. However, the Doge's role was never exclusively military. The Doge's selection process and role in government changed significantly through the centuries, and I expanded upon how that happened in this older answer, which you might be interested in.

The second feature of the Venetian's government, the system of councils, was also subject to a long development process. You can read about that in this other older answer.

I also wrote about the ultimate form of the Republic's government at the republic's height in this last answer which you might also be interested in (and below, in the same link, a brief description of internal conflict in the Republic's earliest history).

Of course, none of the answers I linked are definitive. They're actually somewhat rambling and full of typos! Feel free to ask any other additional questions you may have.

Hey there,

Just to let you know, your question is fine, and we're letting it stand. However, you should be aware that questions framed as 'Why didn't X do Y' relatively often don't get an answer that meets our standards (in our experience as moderators). There are a few reasons for this. Firstly, it often can be difficult to prove the counterfactual: historians know much more about what happened than what might have happened. Secondly, 'why didn't X do Y' questions are sometimes phrased in an ahistorical way. It's worth remembering that people in the past couldn't see into the future, and they generally didn't have all the information we now have about their situations; things that look obvious now didn't necessarily look that way at the time.

If you end up not getting a response after a day or two, consider asking a new question focusing instead on why what happened did happen (rather than why what didn't happen didn't happen) - this kind of question is more likely to get a response in our experience. Hope this helps!

Cool I’m definitely going to read all these links. I didn’t realize the Golden book rule lasted so long! I’ll be back once I read these links 👍🏻.