Why we need to leave the EU can be expressed very simply: Imagine we want a free trade deal with Country X because it has industries that supply us with parts for our vehicle assembly lines. It should be as simple as having a summit and hammering out an agreement. But we have no independent authority to act on trade. So we ask the EU to arrange it.
But the EU says it wants a deep and comprehensive agreement covering multiple industries. Denmark doesn't have a mass automotive industry but they must be consulted on that trade agreement because it makes cheese. Country X doesn't want Danish cheese for some reason, so it proposes a compromise that then has to be referred to all 28 member states. Denmark then doesn't agree, but is overruled. But then Italy wants concessions from Country X because the compromise hurts its cheese industry - so there are further negotiations.
In round two everyone is agreed, but late lobbying means that because the Polish sausage industry suffers from a labelling issue and has successfully lobbied to vote down the package.
It goes back to square one and we spend a few more years negotiating - when all we actually wanted was an agreement that Country X would comply with an international standard in the production of wheel bolts so we could allow imports.
The bottom line is that unbundled "trade deals" - or mutual recognition agreements (ie agreeing to accept that Country X's regulatory standards are as good as our own) happen a lot faster and can be enacted sooner than the EU's insistence on domineering trade deal that often include cultural and political reforms as part of the EU's own quasi-imperialist agenda.
What could have been done and dusted inside a year ends up taking a decade - and we are powerless to speed that up. Leaving the EU would mean we could open up new markets by a process of unbundling, without insisting on more sweeping and invasive reforms.
The EU does it because it wants everyone to think as the EU does - with it's quasi-progressive social agenda. The fact is, Western liberal values cannot be imposed on Africa. We arrived at those values by way of being a first world wealthy country. So if we want liberal progressivism in Africa then we do it by way of making them richer - which independent trade will do far sooner and it will be lasting and genuine.
That is real global participation. The EU is just playing at it and it puts it's own cultural agenda above the needs of our domestic trade. We can be more agile and do more outside the EU and we can show them how it is done. If we want to advance the ideals of liberal progressivism and thus solve the immigration crisis, then we will do more by exchanging goods and dredging shipping channels than waiting around for the EU to modernise. The EU is locked into 1970's thinking and simply isn't fit for the modern globalised, internet connected world.