Here's the rub. 'Ever closer union' does not appear in the text of the treaty of Rome. It appears in the preamble, which is not part of the treaty. Article 2 cites 'closer relations' between the states. Article 3 sets out the activities of the Common Market. Measures to achieve ever closer union are not mentioned.Ever closer union was a founding principle. It's what we signed up to in 73. Don't pretend it's a surprise or something new.
At the time of the 1975 referendum, those in favour made a strong pitch that we were signing up to a trade treaty. Ted Heath said that the treaty was not political. Some years later he said "it was always political". The paper that the gov sent to all households identified money, food and jobs as the key issues. On the subject of sovereignty, the paper relied on the need for unanimity in the Council of Ministers to ensure that British laws could not be decided by "faceless bureaucrats in Brussels". QMV has seriously altered that.
Ever closer union was not mentioned, though "bringing the people of Europe together" was.
The case against membership was most eloquently put by Tony Benn in a letter to all his constituents, published in the Spectator.
https://blogs.spectator.co.uk/2016/05/a-lesson-from-the-1975-referendum/
Benn relied on the argument that sovereignty was lost by our membership and that the EC would continuously seek to enlarge its policy footprint.
Those arguments have continued to the present day and have been magnified each time the EU has taken or proposed more powers for itself.
Did Britain actually sign up for ever closer union in 1973? Did the voters in 1975 sign up for ever closer union? Has the continuous talk of ever closer union carried the British people willingly along?
Remainers who argue that leaving will be damaging economically are probably right, but leavers voted emotionally in the belief that ever closer union was not what they wanted and was not what they were promised.