The EU is a great idea in theory but awful in practice. Most successful federations ( the US, Australia, Canada) leave the minimum amount at the national level - pretty much defence, income tax and foreign policy. The EU (well EEC when we joined) started off well by focussing on trade and movement of labour but has become horrendously bogged down in trying to grab more and more power at low level as well as high.
The whole Euro and economic management of the bloc is a disaster. Joining the Euro means a locked in exchange rate ad infinitum with really successful economies like Germany and the Netherlands. It's been hollowing out the club Med countries ever since (not helped by the poor economic management of the national governments).
Places like Romania, Bulgaria and the Baltics have 20-25 per cent lower population than they did 30 years ago - this is also helping create a two tier EU.
The quality of MEPs is risible - there are some really unpleasant people on both right and left who would attract a lot of negative publicity if they were in the UK parliament. The only upside is they don't have any real power as only the European Commission can propose new laws and regulations so the elections for MEPs are basically a sham.
This brings me on to the EC itself and the 5 Presidents. Two of them have criminal records - Lagarde for financial malfeasance for doling out hundreds of millions to Tapie and Borell for insider trading. Von der Leyen was widely regarded as the most incompetent minister in Merkel's government but was put in place as Merkel's sock puppet. Michel performs the same function for Macron.
Anyone who thinks the UK would be come a rule maker by rejoining with these sort of people in charge is not paying attention. The EU is about accumulating political power without democratic accountability
I like the idea of the EU but it is going to take a massive amount of reform to persuade my to put my X in the yes box to rejoin