I would disagree about Portugal, Italy, Spain.
They have benefited heavily from a common market. And the common currency has made business and tourism a lot easier.
For Portugal and Spain, the EU money for infrastructure has been invaluable.
Now if you point out the pain of the EU parliament and Commission, I’ll agree with you. Ideally the EU should be the EU council of heads of government
You say the Euro has been great for Southern Europe. It has pushed them into a debt trap. Since they can no longer engage in their standard corrective - competitive devaluation of the currency - they are stuck with sky high unemployment, low growth or no growth and crushing debts they can’t repay.
They would have been a lot better off if they still had their national currencies and could devalue them to make themselves more competitive on cost.