They've done a frankly brilliant job of shutting up anyone on the left who spoke against the EU, going back years. Some have been bought off (Kinnock is the obvious example). Some were systematically and constantly ridiculed, Benn etc, and many have died. The modern day left , in my humble opinion, have become less about how to help people who need it most, and more about how to beat the evil Tories. Not a bad thing in itself (beating the tories) but self defeating, as they saw the only way to beat the tories was to ape many aspects of them. Notably their perceived "economic prowess" (a sick joke but one they've happily swallowed for years.)
It's always made me laugh , and then gnash my teeth, that the narrative that only tories reject the EU has taken such a hold in this country. To be fair, they've set the trap fantastically and we've fallen into it for years.
The real joke though, is that in Greece, spain, and much of southern Europe it is the youth (hate that phrase but you know what I mean) and the left of politics that are anti EU. The banks, the businesses, the millionaire (white obviously) agri-businesses (who successfully shut out African and Asian food producers) are the EU's biggest proponents and beneficiaries.
I'm all for the long game. Get out first and foremost, find a real leader who believes in socialism (not a useful idiot ) and reshape the country. It'll take years, maybe decades, but whilst we're in the EU it will never happen.