> High public debt in your own currency supported by your central bank it's not problematic.

Yes but the Euro is not an own currency of any single country which is why a country in Eurozone can potentially go bancrupt. this led to players betting against Italy in the last Euro crisis until the „whatever it takes“ bailout guarantee. Challenge is there now is unbounded spending across Euro countries with no end in sight. It all just feels like a race of who can spend faster until the party is over.