"Your right. But since the EU did not exist then you are probably remembering a different vote. Maybe something to do with a common market?"
This (apart from "Your") is something on which we can agree. There should have been referenda on Maastricht and Lisbon treaties with a requirement for super-majorities to ratify them. That really should be a requirement for any substantial constitutional change. That undoubtedly leaves a democratic deficit to which it's reasonable to object.
However taking an irrevocable* open-ended** decision without requiring a super-majority is simply piling one democratically bad procedure on top of the rest.
* in practical terms
** the terms of implementing it were and still are not defined