Britain's been "investing" for decades and we still don't get much in return. I'd say that's a bad "investment".
It's not too hard to understand. If poor countries become rich and rich countries trade with them, the two economies will expand. We can't know how much the UK benefited from paying dues only because they did pay dues.
That being said, it is the choice of the people what their country does. If the people do not want to invest in other countries, they shouldn't have to. Power to you, Britons.