But it would not be the end of the world.
There are many things wrong with the World Trade Organisation. But they are nowhere near as bad as the things that are wrong with the European Union.
Alas, we are probably heading for a second referendum, between the eventual deal (or not) and Remain.
If the other option is the Single Market and the Customs Union, or the EEA, or the "Norway Option", or the "Switzerland Option", or whatever they wanted to call it, then vote Remain and resume the struggle the next day, just as the struggle was resumed on the day after the referendum in 1975.
But if the other option is No Deal, then vote for that. It would not be ideal. But it would not be the end of the world.