They know what ideological variety looks like; you’re not being deprived it because they can’t think differently. The consensus on British political-economy between the main parties is so unanimous as to run on rails, so among the elite, the struggle is not political but between the managerial set.
You’ve been reading stories for several years now about the demise of the Tories and, with that, Britain’s ‘natural party of government’. The Labour leadership want to claim that mantle and, in their paradigm, it’s a question of contorting their shape to fit the cast, not altering the cast itself.
They want to be the Conservative Party; what that Party embodied, narratively, before it imploded. That they think the smartest way to achieve that is via this route should be taken as an instructive study in how British democracy works and where politics is actually occurring within this system.
I’m old enough to remember newspaper articles from 10 years ago about clever, ambitious and deeply self-entitled twentysomethings swilling pints of expensive lager and talking about how “Labour is an excellent party to get on in” and how they’re “definitely going to stand in 2020”.