It could still be backed by a blockchain - in fact, it would make sense to use some kind of hash chain, because then you have a verifiable and replayable ledger

It could still be backed by a blockchain - in fact, it would make sense to use some kind of hash chain, because then you have a verifiable and replayable ledger / event store / replication log / whatever. It doesn't need to be distributed and/or use proof of work/stake to be blockchain. I totally understand the blockchain apathy though.