Why the EU IS GREAT:
EU promotes fair competition with tremendous collaboration between multiple nation states. The influence of individual members is magnified many times on the world stage, by being part of this trading bloc.
The 'red tape' that many lament, means that the competition rules are fair. Ireland can't undermine everyone else with ridiculously low corporate taxes on special companies. Romania has to provide at least a skeleton of a social welfare state. Spain can't produce or import dodgy electrical goods. A fish I eat in Croatia should basically be safe to eat from an unpoisoned river. There's a relatively level field for agriculture, manufacturing & service industries across the member states, having so many mutual standards. This also promotes highly efficient (cost-competitive on world stage) manufacturing (just-in-time). There is a well-established (& tested!) arbitration scheme in the ECJ.
As an EU citizen working in the other EU countries, you always have a level of minimum rights even though you're not a local citizen. There are mutual state pension & health care arrangements. The rights even extend to voting in local elections. These protections promote cross-border investment, communications, consumer rights, mutual respect and positive cultural exchange. Local culture, traditions and political autonomy are promoted by many EU mechanisms, sometimes trimming power off of national govts.
Frictionless trade especially benefits small traders & local producers (which helps preserve local culture & encourages local jobs in communities that would otherwise struggle to economically). Big companies can afford the faff to deal with complicated customs etc., but small companies would struggle.
I like the Euro too. What a faff it was dealing with so many minor types of currency. Germans may grumble about it but them bailing out others will promote better governance in Greece & Italy in long run, which will make those better places for their citizens to live, therefore likely to be more stable politically.
EU membership meant I could retire to Spain for better weather (I suffer in the cold). Unemployed young Spaniards could go to UK to get work & save up to come home & buy first property, with work experience behind them to help them get jobs back in Spain.