> existing centralized systems

Other comments speak to this - but I wouldn't describe SWIFT (the predominant cross-border payments rail for high-value transactions that you couldn't just throw at a fintech eg. Wise) as centralized.

It's a bunch of hops, across correspondent (but separate) banks, that slow payments down, make them expensive + inconsistently traceable + introduce a bunch of manual ops burden along the way across each of the banks in the chain.