Your arguments are more philosophical rather than technical and real. If we start going down that path we would soon realize that even your being is not decentralized simply because you can philosophically argue about anything and bring reasons why you found truth where there is no facts.
The truth is that at some point a compromise has to be made, bitcoin is decentralized but the purpose of bitcoin was to forfeit the need for a third party to verify the validity of the transactions when making a transaction online, and when it comes to that point bitcoin succeeded.
Now it is true that bitcoin is built over a centralized network which is the Internet, but even if the Internet could be decentralized as well now we need to consider that the Internet runs above the electric grid, which is a another centralized network, so while the OP is right Satoshi needed to begin somewhere, if he had to wait until everything else became decentralized then we should probably had to wait for bitcoin for decades, and that in the best case scenario.