What year was this? The removal of a lot of this financial friction was coming to and end regardless of the Euro or ECB. Didn't Croatia only join the Euro this year? I'm finding it hard to believe this archaic mechanism existed up until Jan 2023, that is to say I find the example slightly disingenuous.

The friction between Ireland and the UK is near zero, both have different currencies.

This isn't to say there aren't benefits to the Euro; on an individual level of course not thinking about exchanging or exchange rates makes life easy. It's simply not palatable to the UK, Brits or the core financial institutions by which its service oriented economy excels.