Ok so firstly you're not the OP I was replying to, so neither of us know for certain whether they were talking about replacing the banking system with a decentralised currency vs keeping the existing centralised private banks and just having them use a blockchain as their database. I assumed the former because of their wording ("replace the banking system"), and because the latter offers no advantages that I know of.

Secondly if you think a blockchain would offer some advantages over other more efficient write only databases, I'd be interested to know what those are, because to me if you're not running a decentralised system then you're only getting the downsides of blockchain (such as it being single threaded, slow, and space inefficient) without any of the upsides.

For some background, I'm well aware of how both blockchains and crypto work, having been obsessed with them for a little while in 5 or 6 years ago like many of us were before becoming disillusioned. I've also got professional experience as a developer on both immutable databases and banking ledgers.