There are proven instances where systems such as this can remain stable. Slavery is one. There are tons and tons of other systems throughout human history where massive inequality remains stable.

In fact inequality is the bedrock of civilization according to our current theories of anthropology.

How do self interested parties gather together to fund great infrastructure projects and technology required for the progress of civilization? People on their own are self interested do not assist others outside of family or tribal units.

What causes people to organize is that there must be a small group of wealthy individuals who pays a Large group of individuals who lack wealth to work together. This isn't something I'm making up. This is the basis for the formation of civilization according to anthropology and there there are loads and loads of research and papers that support this theory so it is currently the best of what we know.

So it is not at all clear that the result is trivial. your conclusion is not at all scientific or logical you're just going off your intuition which is highly flawed.

Isn't a representative government the opposite? When a large number of people work together to decide to funs or accomplish some goal, voting and taxes

No it's not. Any form of government is an attempt at centralization of resources and decisions. It is an attempt to move closer to an extreme system of singular decisions with a single point of resources. You do tend to see these concentrated centralized structures within government. Leaders, central banks, executive branch, centralized resources.... etc. Although It's not fully centralized, the creation of government from no government is essentially movement in the direction of centralization. So in other words:

The point of government IS centralization. The US government is sort of an attempt at centralization with checks and balances. An attempt to make sure that the centralization doesn't become too powerful. A movement towards the extreme but not all the way.

So the liberal western form is not an exercise in working together towards some mutual goal. Rather it is in satisfying some baseline level of acceptance of how society works, property rights, etc. Power comes from the people, not by divine mandate or military might.

>Power comes from the people

Right, but that was my point. Its a step closer to people coming together to accomplish or fund some goal instead of just some rich guy saying "I have money, I'm paying you all to so this now"

It doesn't have to be a rich guy. But some form of centralized rich power. Like a corporation for example. But even complex structures like this involve a cluster of individuals who own the corporation or have seats of power within the structure. This small population of people controls wealth and resources and deploys it accordingly.

In the beginning though, before complex structures like corporations formed, civilization began with rich guys telling poor guys what to do.