WE are not describing the future of routing small packets in 1964, that is NOT the world we are existing in, where "decentralized" meant a top-down hierarchical structure
When WE talk about "decentralized", we mean roughly a spectrum, with "centralized" on one side and "decentralized" on the other
Now I don't think Bryan Newbold realized that when he pulled his definition from Mark Nottingham who pulled his definition from Paul Baran, that this was the case. I think this is a game of telephone.
(I don't know how Mark Nottingham didn't realize it but that's an aside)