Stablecoins are literally central banks. Decentralised coins are literally decentralised central banks. Bitcoin's algorithm is a central bank.

Decentralized central banks - are these the finance equivalent of dehydrated water ?

Well I don't think they're very decentralised, which was the original premise.

Any rules can and have been changed by those with leverage to do so (be that exchanges, miners or devs), in the end any system like this storing value is captured and controlled.