If Brexit were so simple, it would have happened already.
You wouldn't have watered down proposals of how to do it.
You wouldn't be reliant on the EU bending to your will.
You wouldn't have done things like "forgot" that you have to get it past the House of Lords, when if you'd just done that a year before anyway, you could have pushed it through a second time and their objections that time would mean nothing as it could just become law anyway.
There wouldn't be stories about what could happen *now*, that everyone could have told you years ago would happen in this case.
"Amazingly, when we pull out of the EU, all those EU-wide agreements mean nothing any more". Gosh, I'm shocked.
It doesn't have to be the end of the world to be a silly idea.
And if we did everything that 50%+ of people vote for, you'd end up with men having to look after all babies at home, and towns in Sweden voting themselves free money instead of having to work (literally just happened!).
If we're gonna vote on these things, I'd infinitely prefer a vote on "Should we go to war with country X" (with a min 75% threshold for ceratinty), which we never seem to get.