The OP specifically asked to leave cryptocurrencies out of it and judging by the post does not consider finance to be a 'substantial' example. Are there any concrete examples where blockchains are both useful and necessary?
Hyperledger is a blockchain that is mainly used for these private blockchains that are used in corporate settings. However, a public chain has 100% uptime, is permissionless, and is by far the most useful application of the tech.
https://www.baseline-protocol.org/ Baseline Protocol is a collaboration between Ernst & Young and Microsoft to use Ethereum as a secure, cross-enterprise business process collaboration layer, which is powerful but you'll have to some knowledge of how back offices in enterprises currently work in order to grasp it.
Finance is incredibly substantial. Everything you know is powered by finance. It's a multi hundred trillion dollar industry.