There are many measures of success, and if you want to talk about quality of life, by all means look at how bad the discontentment with the EU has been growing over the years, among all member states. Keeping everyone in the EU is not sustainable.
I'm not playing politics, but in my take any movement that distances you from a remote central power is positive in the end. Freedom should have been the basis for the EU, not Socialism. We all know where it's headed now.
Freedom is an investment. Of course the UK will be worse in short run, and I'm sure EU members will poit fingers and say "we told you so!". But in the long run they will be better off than the rest of Europe, where structural changes have proven impossible. Such decisions take dozens of years to give fruit.
GDP's not perfect, but that should hint at a number of things. Look also at Organic Inflation, and Debt Ratio. Unless the UK governments to come take much worse decisions than the EU bureaucrats, it should not be too difficult to do better.
Your economy can boom with all the citizens suffering. For example, if average wages go down, and the rich get richer, the overall economy grows, but is of little consequence to most people.
When countries grow powerful, they begin to forget about the "socio" part of socioeconomics, and just look at dollars.
I have yet to see any data that the Brexit is a net positive for the economical wellbeing of the British people. That is not what I'd define as "Enlightened".
People are sick of biased crap and vague economic theory being touted as data telling them how good immigration and free trade is for them, while in their own lives only seeing things getting worse.
No one has any data one way or the other, and will not for at least ten years. The UK entered uncharted territory. Your guess regarding what the future holds is about as good as anyone's, including those of the experts.
