Why this dichotomy between "non-physical cash" and "decentral currency"? These things are linked, but strictly speaking you don't have to choose between them.

Abolishing physical cash does not imply migrating to a decentralised currency. But migrating to a decentralised currency is probably only possible by abolishing physical cash; I don't see gold coins coming back.

So, how is it different to have your money controlled by a private key, and nobody having the power to seize those money? Ask every single person that has had their account frozen. Whether you think it happens for just reasons or not, surely you agree that it isn't the same as having an ecosystem of digital centrally issued money? Not just issued, but also seized, through courts and police.