The number of people who used to vote but no longer do because is far, far greater than the number of people who vote Tory but might some day vote Labour.
Labour spent at least a decade before Corbyn contorting itself in an attempt to win over the latter, which is the main reason why there are now so many of the former.
The result was almost 4 million fewer votes in 2015 than in 2017, and exactly the same sort of hysterical shrieking in the media about deficits and national security that we see today. And the now likely permanent loss of Scotland.
The only serious way to court swing Tory voters would be to out remain the Liberal Democrats, at a cost of huge numbers of seats to the Tories across the North; or to outright embrace Leave (which is the last thing Labour voters who whinge about Corbyn want), at a cost of swing constituencies like Kensington or Canterbury, and the likely permanent disaffection of anyone under 55 who went to university.
Labour is boxed in because of the loss of Scotland, and because of Brexit. This, far, far, far more than Corbyn's poor polling figures, explains why the party is struggling, and I have still yet to hear a single plausible explanation of how a moderate non-Corbynite would solve either.
It is a far more plausible path to victory to champion economic policies which the rich but woke abhor, in order to win back the much larger bloc of voters who left Labour not for the Tories, but because of Blair-induced apathy.
It was precisely these voters who fueled Labour's dramatic improvement in 2017, who conventional polls do not pick up, and who by many accounts will determine the 2017 election as well:
https://www.theguardian.com/politic...ssing-million-voters-return-leave-swing-seats
They are already suspicious of Labour's support for the second referendum, and can only be won back by bold and deliberately taboo-breaking and tabloid-alarming economic reforms.
Whereas the opposite strategy of watered-down disingenuous economic and social reforms to woo Tories and placate the rabid media will achieve neither.