After all, if the Referendum was so complex, then both sides are equally guilty of 'voting in the dark'. But their points of view are thus logically equally valid/invalid (if under-informed)

Not really, Elisa. True, neither side could actually say what would happen. But in all probability a vote to remain was a vote for "more of the same, for good or ill" whereas a vote to leave was a vote for something different, although we know not what. I don't think those two choices are equally "in the dark".