I challenge your statement that the blockchain has any uses at all - specifically, uses that cannot be accomplished much better and with a tiny fraction of the resources using 1970s-vintage, off-the-shelf, boring technology.

We've had blockchains for thirteen years now - almost as long as smartphones.

There hasn't been one application in that time that has caught on with people outside the cryptocurrency sphere. Why is this?

Immutable logs long predate the blockchain. Merkle trees date from 1979 and provide a cryptographically immutable log - the classic example of a Merkle tree is Git.

Blockchains do contain a Merkle tree or something that serves the same purpose of being an immutable log, but the two big differences are that in a blockchain, each node has to keep the whole tree, and there is a wildly expensive consensus phase, where all nodes must participate to keep this shared consensus tree structure updated.

Except for cryptocurrencies - trust-free currencies with no centralized source of truth - I have yet to see even a single application of "the blockchain" that couldn't be done for 0.01% the resource cost and 1% the programming with a plain old Merkle tree.

But I'd love to be proven false!