To what extent can one blame the current Labour leadership for going down the center-right path, if the population at large, particulary in England, is just conservative?
They tried running somebody on the left a few years ago, and got demolished.
There's two answers for this
There was a 40% vote for a solid left-wing manifesto and campaign in 2017- that potential is still there. If you transplant it into today's results, it's a substantially bigger landslide.
But would Corbyn, or anyone else sincerely campaigning on that platform, win this time, especially with these numbers? I don't think so, for several reasons.
The Tory downfall initially started in May 2020 when the press broke the lockdown-breaching stories. These stories eventually led to Boris' departure, and then to PM Truss, which left permanent hole in the party, which Sunak only slightly patched up. The role of the press in the Labour polling lead is massive. And I'm 100% absolutely confident that these stories would not have been front-page news if it was a left-wing Labour leader as the alternative. It's the status quo option that gave the press the space to have their fun with the Tories.
Second, based on vote share, Tory+Reform should be over 40%, while Labour are under it. In 2019, Farage stood down his candidates tactically to help the Tories. The Lib Dems did not. I believe Farage - with his class background - would do it again this time, if the alternative was a left-wing leader. So with a unified right, that 40% left Labour vote (the best case) still gets a tiny majority or hung parliament, not much more.