It's not online afaik, but Rob Griffiths wrote in to the Star recently essentially arguing that the Lexit campaign always knew the outcome of leaving the EU would be an almighty battle for the future of Britain, but that battle was one worth having and even if lost, the act of Brexit would permanently leave more room for future left reform than staying would have. So in that part of the left's mind it's not about whether there's benefits now, or even in the medium term.
Personally I voted remain because while I actually semi-agree with the sentiment in terms of the direction and MO of the EU it seemed painfully obvious that the outcome of Leave in the way it went down would not lead to a left revival but a long era of chaotic, unfettered neoliberal war on working class people, worsened by bullying from greater powers, which would probably last for most of the rest of my life. I'm still hoping to be wrong.