Hot Take™
Major changes that are hard to undo shouldn't be decided by a simple majority (like the 51.9% who voted for Brexit).
Requiring ⅔ or ¾ majority is also bad.
Time is the key: schedule 5 referenda spaced over 15 years. If 4 out of 5 return a simple majority in favor, then make the change.
In the US, our constitution requires ⅔ of the House of Reps, ⅔ of the Senate, and ¾ of states to agree. Effectively, the dead rule over us unless we have overwhelming support to overrule them.
In the UK, they allowed a blip in public opinion to throw their country into chaos.
Neither is good.