Perhaps. I don't know how it is solved in Humankind. From a game design perspective (not just RP) this system would be much more flexible in my opinion. And yes it has to be improved. What I described here is just a sketch of course.
In Humankind they have four axes which represent the "ideology" of your empire, what are their values, what are the thing your empire consider more important (additional to Civics which represent more specific laws about specific subjects, and civics influencing your ideologies; for example, if you decided land is a collective property, then you lean towards collectivism, while if you decide they must be inherited, then you lean towards individualism).
The four axes are:
Collectivist economy <-> Individualist economy (communism/capitalism simplified)
World <-> Homeland (if you're more open or if you value exceptionalism for ex)
Liberty <-> Authority
Tradition <-> Progress
I think it's a good system (made me think about the Ethics system of Stellaris) and I'm eager to see how everything will be put into place.
From a historical perspective, I don't know if modes governance follow an "upgrade" pattern. I think they often undergo radical change when the current system stagnates. People in power usually want to hang onto that power. They end up going down with the ship, so to speak, because any change to the system threatens the lifestyle they enjoy, and almost nobody does that voluntarily. Conversely, people at the bottom of the current system, whatever it might be, don't want that system improved, they want it gone.
From a roleplay perspective, any time I hit a Dark Age, I feel like I should switch my government to something radically different. Almost by definition, if I've hit a Dark Age, the existing system has failed, or at least reached its limits.
I think the purpose of the post was more: if a government had to evolve "naturally" (instead of during a revolution), what would be the continuity?
And it's a valid question. For example, if we suppose that Athens maintained its democratic system for a long time; once arrived through the Middle Ages, it's easy to imagine than, under this system, rich merchants would began to hold the positions of power and encourage free/maritime trade (especially with the advantageous position of Athens in the Egean Sea and the Mediterranea). So, naturally and gradually, Athens would become a Classical Republic (where all citizens would have the right to vote) towards a Merchant Republic (where the institutions are factually hold by wealthy merchant families, who will then legitimize their rule through some legal systems).
An religious oligarchy during the Ancient and Classical Time, especially considering the importance of religion in some part of the world, could naturally evolve into a Theocracy, where the priests who were the
de facto rulers of the country just legitimize their rule.
The biggest fracture would occur between Midle-Age governments and Modern governments, because the world came through incredible changes at this time so here I don't see a "natural" evolution (especially from Theocracy towards Communism for example). But it's an interesting thought experiment.