What changed
Filecoin: storage was proved. Retrieval was a market.
The paper's hard part is showing that a provider still has the data. Getting that data to a user, quickly, is a different market.
Original thesis
A market matches clients and storage miners. Proofs of replication and spacetime are how the network checks the miners.
What changed
Capacity can be sold and proved without a corresponding retrieval promise. A deal for storage and a deal for fast retrieval are different contracts. Later proof changes need their own citation.
What remains useful
The paper is the citation when a network claims to pay for stored bytes. Ask separately who can fetch them.