It's a bit like anything really. Take the Poll Tax. The people experienced it and rejected it. For all they knew they were jumping from the drying pan into the fire, but they didn't care so long as they got out of the frying pan.
A problem is that, once people had experienced the poll tax and expressed their disagreement with it, it was scrapped and life went back to normal.
With Brexit, there won't be any going back. Not for a generation or more and not with the concessions that the UK has had so far.
JRM & co. insist that a no-deal is nothing to worry about, but still don't grasp that Article 24 won't apply, but which they seem to be counting on. And those who think the UK can simply walk away from their side of the divorce bill (the EU also has obligations to fulfill towards the UK) and retain any sort of credibility are dreaming. IMO.
And then there are those who advocate "technological" solutions to the Irish border, but are incapable of explaining what they might be and how they might work. From everything I've read so far, that may not be surprising as they don't exist