Decentralized is critical to the recipe as well. 'Immutable' centralized ledgers are largely a non-starter because the scenarios you want to use block chain for are zero-trust type scenarios. With centralization, the promise of immutability holds exactly as long as it's convenient for the centralizing power.

In any case, defining public use or accessibility as the metric of relevance of something is quite illogical. You end up with countless absurdities like relativity being worthless and CocaCola being the most relevant invention ever.