You are seeing what you want to see.
The referendum put to the people of Ireland, when I wasn't even born was in relation to;
https://en.m.wikipedia.org/wiki/Nineteenth_Amendment_of_the_Constitution_of_Ireland
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most notably by changing
Articles 2 and 3 from the previous claim over the whole island of Ireland to an aspiration towards creating a
united Ireland
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The text //did NOT// ask the people of Rep Ireland, do you agree to merge with Northern Ireland, upon their sign off. So......that text you reference is diplomatic "idealism" speak...you see the "aspiration"? Dream world and reality are very different questions. Of course everyone would like lots of things.