Hey, anyone can change in more than 40 years!
Yes, this is the major problem with Labour - they have a leader who at heart is a Brexiter, while his party largely ain't. And whatever they do, short of a People's Vote on any deal (did you see the cheers for that on Question Time, which normally has a hand-picked pro-Brexit audience?), there is very little they can do, and no time left to do it.
However, as you said above, the circle really cannot be squared.