> It's not the concentration of wealth, it is the concentration of power.
Those are the same thing.
> The problem with highly centralized economies is that as an economy grows beyond a trivial size it's impossible for the centralized system to manage the flow of information from the edges. It doesn't scale.
That was true a few decades ago. Now with everyone having a smartphone in their pockets at all times and the amount of computing power we have it should be doable. Still not easy for sure, but not impossible.
> Also, honest competition is good for optimizing your resource allocation
Think about how much non-productive work has to be done just to enable competition. Instead of one organization per industry we need multiple, all with their own overhead costs. Every company has to do their branding, HR, marketing, etc. The whole advertising industry pretty much exists only because companies try to get an edge with propaganda instead of improving their product. Wasted work.
Competition also forces companies to do unethical things. Say one company starts cutting down rainforests to get an edge over the competition. Now they're cheaper than other businesses, and every business that wants to survive has to start cutting down rainforest. One country gets rid of worker rights -> businesses move there and other countries must follow suit. Same with taxes.