Why would a CBDC (Central Bank Digital Currency) be good for the economy? I've read about CBDC, how it could be a cryptocurrency like digital payment system, that could replace fiat currencies. But what I don't get is what value would it give to the economy?
Someone who works at a Central Bank explained to me, that by holding the a currency in your own crypto wallet, and not not as a deposit in a commercial bank, the commercial bank's balance sheet would shrink significantly. By shrinking, it could lend out less money with higher interest rates, and could disrupt the complex commercial banking system in a bad way.
There is good summary (with references) of the benefits of CBDCs on Wikipedia.
With respect to banking sector disruption see this 2018 report by the Sveriges Riksbank. It finds that

while a given outflow of retail deposits into e-krona
reduces banks’ liquidity portfolios and worsens their funding
profiles, banks can normally control this outflow via deposit rates.
Banks can also issue more market funding to restore their liquidity
and funding profiles.

That said,

The exact features of an e-krona can, however, be controlled by the
policy maker. In sum, we do not find any decisive argument against the
issuance of an e-krona when studying financial stability effects on
banks.