Although I agree with everything else you wrote, I don't think this follows.

As a counterexample, Secure Scuttlebutt was created for a specific problem, which was that the creator was a sailor and wanted an offline-friendly social media platform. By using a blockchain, users would have a copy of the database locally that they could interact with and then synchronize when they either cross paths with other sailors (because as long as there's a local network, they can synchronize with peers without the need for internet access) or reconnect to the internet. In this case, the blockchain is relevant in that it enables the network to work independently of internet access and provides decentralized eventual consistency guarantees. A centralized solution would unavoidably require internet access.

It's not a million-dollar idea, and further development is fragmented due to there deliberately being no centralized leadership of the project, but it seems to fit its intended niche use case.