Already after Brexit I've heard quite a few reports of 1) young Brits elsewhere in Europe becoming much more engaged with politics because 'now it matters', and 2) Brexit voters who now regret their decision because it affects them negatively (or is likely to).
Again, I agree with you and I don't think it's ideal, but part of me feels letting people make decisions like this, even if I personally think they're (often) stupid decisions prompted by populism, might be better than jamming 'the educated choice' down their throats.
But I'm not expert on the matter. Are there any historical analogues that might provide some insight here?
It sounds mean, but as you are saying - we have to allow that at least sometimes, so people are ok with listening to more educated people next time. Because when even such fragmented group as economists agreed universally that Brexit is bad, it just is bad, and people should accept it.
I don't believe for a second that people will. There are groups of people who don't give a crap about "being better off" - they care about showing those damn Spanish/British/French/German/Polish/<insert group name here> what they think and being able to "finally decide for themselves" which is complete nonsense. If people could so easily see the benefits of staying together then Brexit wouldn't happen and we wouldn't be seeing nationalist movements all over Europe nowadays. The problem is that the benefits are not obvious and you have to actually educate yourself a bit about them - but if someone is unwilling to put the energy into it, then it's not going to happen.