At the "extreme left", we have absolute anarchy

Didn't humanity start of in this state of "Anarchy"? Isn't this state the basis of all social evolution that came afterwards?
Anarchy is the law of nature until now, and it has proven to be the most beneficial for all species on the planet...except humans?

these autonomous, interacting agents sharing the aim of personal betterment

I think humans always have been living and growing up in small Family like groups and communities.
When did humans every acted autonomous by them self without forming a Family or small community like structure?

When you divide responsibility, some people end up in charge of "making decisions". they get to wield power. Power becomes "centralized" in these people who the society has (more or less aptly) selected to specialize in decision making.

Yes, somebody has to make the decision. From a society stand point its only the question if all participants in this project are making their decisions based on free-will and freedom of choice or does the "Man in Power" enforces his will to other people???
I'm more for a free society where people in charge rotate and are not able to enforce their power on others.

We have experienced in the past half century the benefits of centralization. Wealth and power have accumulated in the hands of ever fewer people, of ever bigger and more dominant companies and organizations. The search for effectiveness and efficiency begets "centralization" - i.e decision-making power accrues to those best equipped - or more willing - to make decisions.

Yes, centralization has some advantages, but in the long run we recognize that our leaders have transformed into a Mafia like structures where individuals care more about their personal well being than the problems of society. Not the most competence and wise people get elected, but more of those politician within the existing power structures get elected to the top.
The abuse of Power is IMO just another symptom of the undeveloped mind and psychology structure of humans. We need to stop encouraging people that these behaviors are good things to go after. Even though we know it better, humans where not able to overcome our personal weaknesses to strive for more power, money, fame...etc... all bad human emotions and behavior have not been addressed and corrected in the past. That's why I often have the picture in my mind of an Ape with an A-Bomb in its hands. We have mastered Technology to a very high degree, but our human personal evolution is still stuck in the Stone-age. So, I would suggest to work more on the condition of the human mind to evolve the society as a whole to a new level.