> One quiet place where blockchain makes sense is shared ledgers between large financial institutions,

https://en.wikipedia.org/wiki/Payment_Services_Directive

Usually refusing to share information or API is a business choice. Besides, once you have a closed group, you just have signed transactions ("permissioned blockchain"), and can (must) ditch proof-of-waste. So it barely resembles what people normally think of as blockchain and starts to look more like signed git commits.