Tether devs probably read the whitepaper until "Digital signatures provide part of the solution", skipping the "the main benefits are lost if a trusted third party is still required to prevent double-spending" part.
but then you also like crypto that is 'stable' which means 'pegged to fiat'?
Not only they aren't "pegged to fiat", but this automatic consideration that fiat is stable is a nonsense. Have we seen what's going onto this world since
2020 the beginning of fiat currencies? There's no fiat currency that has retained its value. Even "strong" economies like the US, UK, EU, they're all experiencing massive devaluation of their currencies everyday.
Unless a stablecoin exists that is pegged to 'purchasing power', which I don't think exists as an established index or anything like that.
A stable coin whose exchange rate looks like 1 coin = 1 hash is definitely not stable. The more the purchasing power, the more the supply, ergo the less the equilibrium price. If only we could find a way to determine that the supply will remain the same, regardless of the energy spent, with some kind of variable parameter...

They could just as well have used a central database instead of a blockchain.
I'll have to argue they don't. Blockchains have full transparency and an established monetary policy. You have neither of those in USDT.