Governance (avoiding forks) and simultaneous transactions (avoiding some forms of fraud) are actively being worked on. Give it a minute.
The biggest benefit of blockchain isn't zero trust, but distributed trust. The zero-trust piece is kind of a lbertarian fever dream that has been tied to blockchain that I think is wrong headed. If you tweak it though, to be distributed trust, then it's a tangible benefit.
To use the buying and selling of valuable art example. You're right, this implementation is bad. It's not distributed, it doesn't really solve any problem. If they tweaked it though, and created a consortia, it could be good. Imagine an "Art dealers collective" where they used an OSS blockchain implementation (maybe Decred with Politea?) to store their blocks on a partially permissioned blockchain. Anyone can read it, but only verified dealers can write to it. They add the ability to add photos, videos, etc and have them validated on the chain, but are probably stored off-chain.
Any dealer who wants to buy/sell with it participates in the chain and runs a node. If any particular dealer does shady stuff, it happens out in the open, making it more likely to be found. If a dealer goes under, their records don't disappear , but maybe their off-chain documents do. Incentivising off-chain storage of extra data is still a problem, but probably solvable. If a buyer in the US wants to validate transaction history for a particular piece, they just ask the system, rather than running down numerous dealers all over the world. If something seems fishy about a piece, you can view the previous pictures / whatever and have confidence they haven't been tampered with.
There's lots of value being added here. They just didn't build it right, and that's not blockchain's fault.