Ultimately, it comes down to the euro, without which there would be no problems. Was the euro itself a mistake? No. The crisis only illustrated that the euro had been created within an incomplete institutional framework. However, we should not forget what we owe to the euro. Before Monetary Union there were repeated economic shocks owing to strong fluctuations in exchange rates.
That created trade barriers. In addition, you must always consider the alternative. Take Germany, for example: without the euro, the currency would have risen very strongly in value during the financial crisis. For a country that exports a lot, that is a problem.