IMO the issue is that Tony Blair so comprehensively changed politics that parties can't win elections in the UK anymore from a leftwing platform. The alternative is that the government/Starmer are sitting there being told that a leftward move is significantly more popular than their current platform, and that they are - suicidally - ignoring that evidence due to ideology.
How would one square the implicit suggestion that Starmer is taking bold ideological stances with the fact that the one thing everyone agrees about him is he lacks a clear ideology?