"at the time of the referendum the EU accounted for approximately 16-17% or world GDP and declining (in the 70s it was 30% plus), that means that 83-84% resides in the rest of the world; I back trade with the rest of the world unencumbered by EU protectionist crony corporatism; a small percentage of something big is probably going to be worth more than a large percentage of something small and getting smaller in long term."
And if all trade ignored geography and other factors you might be right... but it doesn't.
One of the other factors is a similar regulatory environment. A trade deal with the US, for example, will almost certainly require opening UK food markets to products that cannot pass EU and current UK food regulations for things like chlorine washed chicken, hormone raised beef, etc... which would probably sink most domestic producers unless they adopted similar techniques.
Your choice, but don't pretend it's a trivial or obvious issue.