The sole purpose of blockchain is to prevent double spending without a trusted party Other proposed applications are mostly dumb / misguided, like immutable storage, social network posts, etc, these can be done with hashing or digital signatures alone If you have a better way to avoid double spending than blockchain folks woukd get very excited. Traditional database can’t do that (requires a trusted party)
Since BTC/ETH/etc is only “valuable” because of wild speculation and greater fools, the “value” part kind of collapses, leaving the “currency” aspect moot. Which brings us back to “no value”.