It may be the case that the fundamental, key, killer features of the blockchain have lost their initial lustre to many people, and I understand that. But decentralization and verifiable, consistent truth are a really, really big deal.
There are applications with promise, large promise. Killer apps? Maybe. They will arrive, it's more "which of these" and not "whether these":
"At the Ambrosus project we aim to radically improve the global supply chains by creating a trusted ecosystem where we can reliably record the entire history of products and execute commercial transactions accordingly."
Prediction markets -- fascinating stuff with major potential.
* https://qz.com/1163660/brazil-may-write-new-laws-based-on-da...
Brazil experimenting with laws/petitions on the blockchain
... There are many amazing use-cases.
The reason this YC article was published is because there is a great demand for blockchain from investors.
Ignore it or doubt it at your own peril!
If the transaction is on an immutable public record, the authority couldn't say: "Well, no you didn't pay us. Pay us again, or we'll steal your dog."
If you live somewhere where Government/Corporation are out of control, this sort of safe guard has major benefit.
When VisiCalc was demo'ed there were people lined up literally pulling out their checkbooks and offering to pay almost limitless amounts of money for the prototype. Spreadsheets had insane value to accountants.
Other than the core use case of currency that I mentioned, where are the "killer apps" for block chain? A lot of it looks like minor and dubious improvements or solutions in search of a problem. Neither of those comes close to justifying the insane amount of money and resources being poured into this area.