The new thing with blockchain tech is that we can now enforce invariants on state transitions in a decentralized manner. Paired with non-interactive zero-knowledge cryptography, we can also enforce those invariants while keeping the confidentiality of transactions.

The tech is rapidly improving and it’s pretty easy to see where things are going from here: soon we’ll have general purpose decentralized databases where data is open as open source code is open. In fact, state-of-the-art smart chains can be viewed as special (financial) purpose decentralized databases.

As to why decentralized databases are desirable: imagine if you could fork databases like you can fork code in a completely permission-less manner. This is how web development would look like:

You, the programmer, take a look at a public data schema (eg. a smart contract that implements the ERC-721 interface) and decide to build on top of it. Then, a user, who has already interacted with what you built on, decides that they like what you built and lets your app use their data. You, the programmer, can be sure that the data you built on remains available, and the user can be sure that they'll be able to port the data produced by your app into new apps.