In short, from a pure technology and user experience standpoint, using blockchain for a CBDC is bonkers. CBDCs should instead be based on a traditional centralized architecture.
Various officials and news sources report that in the Johannesburg Declaration of 2023, the leaders of the BRICS countries agreed on the need to increase the volume of mutual settlements in national currencies. And the participants of the XV BRICS summit agreed that such an independent payment system will be based on blockchain.
Why do you think that this cannot be some really new single currency based on a closed blockchain, which the central banks of the BRICS countries will have access to, or a ledger in which all transactions of states with each other in their own fiat currencies will be recorded? This does not have to be a fast system, because payments will be made between corporations (international payments are not fast now), and not between ordinary people. The use of blockchain in this case can increase the level of trust between the participants.