Ask Croatia, Ireland, Cyprus, Estonia, Finland, France, Germany, Latvia, Lithuania, Luxembourg, Malta, Slovakia andSlovenia if they are? Hint, they absolutely are.
Any union with such a variety of policies will have winners and losers for every project and legislation. Sometimes that will be individuals, sometimes countries. The point is that most are better off in general and that every country is better off from the sum of policies.
Countries have less control of their individual exchange rate. That was problematic for Greece, who underwent austerity, successfully I might add as access to the EU wide economy and trade, including (over)tourism is what's taken them back from the brink.
In terms of larger countries, it has been beneficial for France and Germany, less so for Italy, but also less of a problem and less of the fluctuations the lira used to suffer.