While your point is valid, I think the "propagate all ledger entries to all nodes" kind of decentralized is different than the "route around broken nodes" kind of decentralized. I'm guessing GP meant the former not the latter.

The internet isn’t decentralized the same way: you have single authorities managing routes, DNS, etc. and - critically - unlike blockchains you aren’t trying to have a single global consensus across the entire system. If my ISP updates my IP, nobody else needs to see and process a transaction, there’s no quorum, etc. That trustless design is what makes blockchains so expensive to use.

The internet isn't really decentralized and realistically it cannot be.

Submarine cables are owned by companies, T1 ISPs provide the majority of routing and you really cannot prevent any of this.

Centralized control is somewhat required because submarine cables cost money and transit costs money and small companies simply do not have the capital to do that.