I think John McTernen's article in the Guardian today makes some excellent points. Here is an extract

It happened because Starmer is listening to focus groups of swing voters. But the brutal truth is that there are no swing voters left – when support for the Tory party has fallen to 25%, there is no longer a pond to fish in. You’re convening groups of voters who are undecided whether to vote Tory, stay at home or opt for Nigel Farage and the Reform party. Sure they have views on what would make them listen to Labour – but they will never switch.

The priority for Starmer is to talk to the 45% of the voters he has won over and to reassure them that he is the change they want to see in the world of British politics.
...

That’s why Starmer shouldn’t give the Tories any quarter. A simple two-line manifesto is all he needs: “Get them out. We will fix it.”

“No complacency” is a crucial position for any political party. But the most dangerous complacency of all is to take your own voters for granted. None of the voters who are currently supporting Labour are wavering because they are worried that Starmer is insufficiently respectful of Margaret Thatcher. They want the Tories out. Labour needs to make that its rallying cry.

I am very much of the opinion that Starmer has worked very well and hard to turn round the massive gap from the 2019 election, though greatly helped by the incompetence of the government that won.

But there comes a point where he needs to be speaking to the people most likely to vote for him, not just the people in the middle. It is a glib over-simplification to say Corbyn mainly spoke to those who would vote for him anyway. Starmer hasn't made that mistake. But he is at risk of not talking to them at all.