The current system where every user is a network node is not the intended configuration for large scale. That would be like every Usenet user runs their own NNTP server. The design supports letting users just be users. The more burden it is to run a node, the fewer nodes there will be. Those few nodes will be big server farms. The rest will be client nodes that only do transactions and don't generate.
In that case we have centralization. In that case, who guarantees that so few people won't come together to alter the issuance of bitcoin. The bitcoin issuance schedule and the decentralization to keep the schedule unchanged is why most of us are here in the first place?
Decentralization does not mean every single bitcoin user runs a full node. It just means that no single user, individual, group or other entity controls more than 50% of the network. A few hundred people or organizations spread over a dozen countries controlling the entire bitcoin network still falls under the umbrella "decentralization", and is still as secure as today, if not more likely more so.
Besides, are you really going to argue with Satoshi?