What changed
Corda: a shared record for parties who already have a contract.
The design is not an open membership network. It is a way for known firms to share a state they can both check.
Original thesis
Only the parties to a deal see that deal. A notary orders the states that might conflict. The legal agreement is not replaced by the ledger.
What changed
R3 and the firms that used Corda treated it as market infrastructure, not as a public coin. Later versions changed the distribution model. A Corda network is still a membership decision.
What remains useful
Use the paper when a buyer wants shared state without publishing every transaction. Ask who the notary is, and which contract a court would read.