hmm...I find all of this an overcomplication of the central organising principle of modern British politics.
Quick summary - it's only up until 2010 but we can fill in the blanks (and in % terms, 2005 was MUCH closer than most recall at a 3% margin, so there really is a correlation):
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And we all know the best ways to get good political coverage in the billlionaire-owned press.
I totally agree with anyone who says that it's all about messaging. But in terms of the imbalance of media favour (I'm sure someone can find equivalent media stats for 2017, and it will be overwhelmingly Tory) Labour in 2017 did pretty damn well to lose by just 2.4%. it is a virtual impossibility to win with anything close to a left-wing economic policy - not because these ideas are inherently voter-unfriendly or anything else, but because they are billionaire-unfriendly.
So yeah, Labour needs to move economically rightwards to win an election, but that's simply because we live in a country where the super-rich call all the shots. Any other considerations pale in importance next to that. It's like conducting a complex tactical analysis into why Watford don't finish in front of Manchester City in the Premier League.
So Burgon might have been 'owned' in that interview with noted thinker Kay Burley (who I don't actually mind so much because I seem to recall her being quite scathing to Tory politicians too), but the point is that Labour did vastly better in that election than anyone would reasonably expect, based upon the media disparity and the impact that had on elections over the previous 25 years. Also, the polls *were* a poor guide to the result in 2017, to the point where everyone was proclaiming that polling was dead. So the idea they suddenly became valid again is a bit much - though in 2019 they seemed to predict it sort of well, so...Lazarus.
Last point of what has become a rant: it's very easy to make people look foolish on TV, which is part of the reason politics by media is such a shitshow.