I think the largest issues with the EU is that it is fundamentally flawed for one main reason: all these countries are tied to the hip to each other due to the currency and singe market, but cannot control the others economies or spending. It's like splitting bills with your unemployed brother in law.
For a common central bank and currency union, each country de facto has to give into a federalism of central debt issuance and budgetary powers. We have this in the United States: the federal government can run a deficit and print money, individual states cannot. We have a republic and California (most populous state) gets more representation than Wyoming (least populous).
For the EU to work long term, every country is going to have to give up more and more power / fiscal autonomy to Brussels each year for the currency to work. What happened when Greece was going to default on its debt? Germany stepped in, bailed them out, and started stealing their assets (airports, ports) because they weren't going to let the currency tank. Granted, Greece has some issues but whether they like it or not Greece defaulting on their debt affects the whole currency block. Greece issued its own debt.
The reality of the eurozone is that it has made rich countries exports cheaper (Germany, France) and made marginal countries poorer (Italy, Spain, Portugal).
If you grew up in Croatia speaking Croat and possibly English, do you really think the Greek labor market is open to you? Could you in all practicality relocate to Belgium and start a business?
Anti globalism sentiments are in every country these days. I personally don't see euro countries giving any more power to the European Commission, and I see the project ultimately failing.
My 2 cents. I don't have a dog in this race, and don't really think the EU is "good" or "bad."