that 'Brexit' has nothing to do with leaving the EU in a considered, well supported manner involving comprehensive planning and with clear and substantive evidence as to why leaving will be so much better than remaining
Ah, you mean the same planning and evidence that we had when the politicians signed us up to the EU in the first place in 1992? "Let's build a political union, it'll be soooo good ".
They generally seem to feel that there is far more to be gained by constructive membership
They've been singing that song for 25 years, and what did we get? An EU that is ever-more autocratic and suffering more and more under the rise of anti-EU populism, yet the only solution the "constructive membership" can come up with is "we need MORE EUROPE, that will fix everything".
The leaders of the EU are deluded autocrats living in denial in their own little world, dreaming of running their European Empire, and completely unable to see that the ordinary people are less and less happy about it. There's nothing constructive in that behaviour.