It can be to different degrees

1. Connect to 1 relay (centralized)
2. Connect to 7 mega relays (a bit less centralized but arguably still centralized)
3. Outbox model, 1000s of community relays: decentralized 
3. Outbox model, lots of people running their own relay: a cypherpunks-wet-dream decentralized

The flexibility is the most interesting thing to me