You’re right IMO about the problem facing the Tories.
But you’re wrong about Starmer and Labour. In the same way that Blair was able to sideline the Labour left because power was finally in sight, so with Starmer. But the left came back during Blair’s and Brown’s and Miliband’s times in charge. It then took over. And it will come back to haunt Starmer.
Benefit cuts, lack of willingness to subsidise or bail out loss-making industries, fuel prices, Israel, relationships with the US, NHS reform, military aid to Ukraine, and very possibly military intervention elsewhere, net zero costs to ordinary voters, these are all flash points. There will be others. And the tendency to move left isn’t an intellectual, considered position; it’s an emotional, populist one. They’ll be back.
Which leads to splits. Any more WFA style policies and it’ll be sooner rather than later.