Seriously though, there seems an implication in what you are saying that either Brexit is a less intelligent option or that voting for it is somehow a harking back to bygone times rather than a looking forward.
Well it is possible that some people voted for it for those reasons and obviously the whole issue is a matter of opinion but I would refute it is about either of those things.
At its base it is a simple consitutional decision that will have us back in line with our history (Britain has spent longer as a separate country or union of the British countries than as part of a European federation, and , as empires build they surely die away again and that is IMO what is likely to happen with the EU over the next 10-15 years).
I think once the initial effects are over we will be better off and better admired out than in.
It's hard to see how things really change a great deal though. I mean if you examine what 'trading with the world' really means, you're essentially talking about government levers, as obviously companies can trade with whomever they want already.
So, you have tariff related instruments, which are quite self-explanatory, and non-tariff related instruments, which are things like standards harmonisation and migration agreements. In all likelihood, any such deals struck with other countries will bare a very strong resemblance to the one we had already with the EU, or no deals will be struck.
If we are part of a global system of trade, then there are a great many non-tariff related things that are best set on a global level to allow for fair competition. Things like employment, environmental or quality standards, for instance. So the notion that Britain will be sovereign over everything and no external party will have any influence on how we function is unlikely unless we opt out of global trade.
People harp on about bring governed by Brussels, but most of the regulations are around eminently sensible things. Even when we leave, there will be regulations that remain that dictate how Britons in Europe can access 'shared services' in the same way that EU nationals here will hopefully be able to.
I think if the EU fails it will be an incredibly retrograde step for European society. You mention that it's existed for a relatively short time, but its existence coincides with a period of peace in Europe that we have never seen before. I've no doubt people will argue that is purely a coincidence, but throughout history, European states have fought one another because existence has been competitive rather than cooperative. You can see the tone of discourse already returning to spikiness and we haven't even left yet.
Theresa May poured scorn on 'citizens of the world', but that's what everyone is. We're all human beings, and all have an enormous amount in common. I really hope we don't forget that.