The closest technology we have are verifiable databases, usually immutable ones. They can detect the server modifying the data, either with a Merkle or vector c

The closest technology we have are verifiable databases, usually immutable ones. They can detect the server modifying the data, either with a Merkle or vector commitment tree, which blockchain technology also relies on. The difference is that those databases are much more efficient than blockchain technologies. The whole proof of work (voting power depends on computational effort) song and dance is unnecessary for a database. Even for a distributed database you only need a Byzantine agreement such as Paxos, which can only tolerate a certain number of faulty or malicious nodes. This would not work for cryptocurrencies, they need to tolerate arbitary number of such nodes (also known as a Sybil attack) to avoid the double spending problem. Cryptocurrency transactions are not I-confluent (invariant confluent), but certain database transactions are and they don't require consensus at all, so there are specialized databases that can tolerate arbitrary number of faulty or malicious nodes without Sybil countermeasures. The problem with crypto is that a solution to a specific problem (eliminating the double spending problem trustlessly) can't be applied to every problem. There are trade-offs involved. Solving the double spending problem will let you have cryptocurrencies, but will lock you out of efficiently solving a lot of other problems.