OK, so I'm going to highly overgeneralize here, and will primarily be using Bitcoin and Ethereum as frames of reference.
A block chain is basically a network of computers that all agree on the state of a linked list database that basically is append-only.
There's some game theory that keeps all the computers basically following the same ruleset of how more blocks (sets of new transactions) get created and propagated to everyone in the network.
Smart contracts are just code baked into the block chain that a network node can run and get a result. All these "items" and things are just resulting computations of the contract. I think these are cool because we can make the money programmable in some very limited ways.
You're also right to be skeptical of other points of centralization and how they get overlooked.
Where is the use? Because you're right, having a large network of computers maintaining and continually syncing a redundant data set that can't be tampered with is significantly harder than a sql database. Well, you have to trust the database maintainer that they didn't do anything suspicious, and banks are incredibly suspect institutions. Well, what about cash? That works, but it's highly impractical for the internet age. With a crypto wallet, you can have internet money you have full control (and responsibility) over.
It has some niche use cases it is great for like cross border remitences.
Being in favor or support of the status quo is also pushing an ideology.