Bitcoin is a decentralized digital currency, by decentralization they don't have any middle man that control it's operation. The performance is based on peer-to-peer people around it's ecosystem, the network security is also dependent of the people around it.
CBDC is a stable digital currency that central banks like to issue, it is going to be control and manage by the central bank, it's affairs are not restricted by commercial banks, anyone can use it any where and anytime but they are regulated in a such a way that you can be restricted if you violate any rules of the CBDC, this is Hy it's not good to use it in the first place because it's not your key or your coins.
Stablecoin work in this manner. The difference between CBDC and stablecoins is that one is control by central banks and the other is controlled by group of people that form a company.
However it's true that stable coins are not far from CBDC. For Christ sake they shouldn't bother on creating CBDC anymore. This is only an added waste like a meme coin/shitcoin. Nice comparison though between CBDC and stable coins. Many are for sure can learn with it. BTW, another difference of CBDC and stable coins is that there are also some stable coins who are decentralized. DAI is one popular decentralized stable coin that I know.