"All you get" is a distributed & anonymous consensus algorithm that's resilient to malicious actors.

That is the value. If you don't need these properties, sure, you don't need blockchain.

As for the maintenance cost: Proof-of-Stake is making interesting progress. There are initial ideas around not having an entire copy of the blockchain.

I'm not aware of commit-time reduction work, but would welcome pointers. (Either way, you'll always have a commit-time issue in a distributed system. You might reduce it somewhat, but it won't go away.)