Hey, @revisesociology.
Yeah, you did do kind of what I did, except you broke things down better, I think. How you define decentralization is a little different than mine, too, which I guess makes both our points. :)
I like the idea of the ecosystem. However, you still have dominant species, which you refer to as top feeders, and they can pull a significant amount of the resources in an ecosystem to themselves, and the rest of the animals can be helpless to defend against it. There are some who manage to overcome great odds, though, too. In the case of those animals, it depends largely on their own strengths and weaknesses, and who they run with.
Generally, though, ecosystems don't filter out the negative, but except them as a whole. And I guess what I mean by that is, the predator will probably end up with prey for dinner. Not so great for the prey, but the predator lives for another day.
None of them own the ecosystem, but some can certainly control it, or highly influence what others do within it. So, even without conscious thought, like a human should have, things tend to centralize to the smallest denominator.