It is a known fact that one's vote is but a tiny fraction of influence over the way in which the country is run, should we dispense with democracy altogether?
Even after Brexit, you would still be stuck with an interconnected world making decisions in real time. How much influence can Britain, possibly without Scotland, leverage on the global stage then?
The Leavers aren't spelling out very clearly what a post-exit Britain would look like, or how it would deal with the wider world.
Should we throw our lot in with the US completely? Maybe realign to China? Follow the Japanese example into several lost decades? Commonwealth? EFTA or not? If not, how would we then trade with Europe... tarrifs? What would be the cost of implementing new trade deals, who will manage them and will we lose or gain from the transition? If the EU investment is pulled, will the government step up to plug the gap? More austerity? Where will the jobs created by large European companies relocating their operations come from? If we do go the EFTA route, then how would Leavers justify the status quo on immigration that would entail (minus permanent settlement rights) to their supporters? You can go on all day.
Their camp is too hopelessly divided to even begin answering any issues of substance, and I doubt talking only immigration will swing it for them -- it's a toxic topic.