I assume your question is mostly directed towards Britons?
But there are many EU-skeptics within the EU, I being one.
The trading union of EEC was a great idea! Wonderful, can't get enough of it.
It makes a whole lot of sense to implement common rules and regulations for European countries, which helps to ease trade and movements within Europe. That's good for the economy and good for the political stability and therefore peace.
It's also good to have a co-operating Europe to counter political and economic challenges world wide.
However, Europe is immensely diverse! It's ludicrous to impose identical rules for countries so diverse as say Bulgaria and Ireland.
Rather than becoming a Nation, EU should have remained a confederation, where the individual countries voluntarily signed up to what suited them, rather than having compromises pushed down their throats.
The EU-elite and the most ardent EU-enthusiasts tends to be those who are fairly well off, who can get a job in another country, who travel widely, who think of themselves as being international and in so many way they have completely lost touch with the majority, who actually like their country, their culture, who are genuinely worried about their jobs, if they have one. Who are worried about their retirement. Who can't afford private insurance to compensate for the welfare societies being rolled back. Who face the problems of flawed integration on a day-to-day basis and whose retirement age has gone up.
These people have way too often been dismissed by the EU-top as ill-informed, ignorant, narrow-minded xenophobes. - So of course there will be a reaction.
I personally don't feel I have much influence on the EU-Parliament and I don't feel they listen to me at all. So why not sack the whole bunch and start again?