Centralized databases are faster. Centralized consensus is dangerous for the same reason that a dictatorship is dangerous. The organization in charge of said solution would exercise dramatic control over the execution of said code. You need not look very far into the past to see egregious examples of organizations abusing their centralized position over data. I shudder the thought of a centralized actor having the same precise control over all monetary transfers.

Meanwhile, the banking system itself is not centralized. It's quite slow to settle monetary transfers from bank-to-bank.

Right now, Lightning Network is live on BTC's chain. It's instant, near free, and yet it's decentralized.

Look at how certificate transparency is done.. a few servers using same protocol is all it takes.

Most crypto-things have this idea that they servers validating transactions have to be compensated and that anyone can do this validation. (validation == mining)

Having a few well regulated entities do all the mining is a centralized system that can be verified externally. Without all the cost of decentralization. And with the added security that validators are trusted entities.

There are rarely completely centralized consensus. You have different sides which for better or worse create consensus together. You have a law, prosecutors, activists. Sure you have corrupt politicians which centralized power a lot but this would is a problem for crypto space as well because of the people will access crypto through a classical business which can lobby for own interest.

A settlement of a crypto payment is much faster than a credit card payment in terms of settlement time. And a credit card payment is centralized.