There is a large constituency against the status quo in the UK. We have proof of that in the 2016 Brexit referendum, where 17 million people voted strongly against the establishment line and effectively against an economic model that we had had for 40 years. People voted in part to take back control, and what is nationalisation of basic aspects of our lives like water / housing / energy / drug manufacturing / transport etc if not taking back control?
Since the pandemic, the implementation of a chaotic version of Brexit, and the cost of living crisis. The underlying aspects of the 2017 / 2019 Labour policies are even more starkly relevant. Everything has been laid bare, and for some reason the two main parties are now completely devoid of ideas or vision.
Corbyn was hard left in a distinctly centrist country whose "Left Wing Party" is (despite its roots) very much left-leaning centrist, and who's only ever seen real success while occupying the middle-ground.
> voters want something like Tory-lite. Blair did that and no one wants to go back to it
If nobody wanted to go back to it then we'd have Rebecca Long-Bailey as Leader of His Majesty's Most Loyal Opposition, not another centrist.