Distribution effects mean that for some communities and individuals it will be a massive change. Barely viable hill farms or small fisheries go from being viable to not.
There will be some success stories as well, some might be dramatic.
Most of the "catastrophe" stories came from gammon strawmen though and not remainers, like:
Remainer: it's likely that over the next decade brexit will result in the average person in the uk being 5% poorer than they'd otherwise have been.
Twat: this is project fear, we won't end up like Somalia just because we stand up to Brussels.