A lot of that is just the 2019 manifesto positions compared to later positions. Something that's come from the internet age, and the amount of historic archive material that can be easily accessed, is people now think politicians have to say all the same things forever and never change their mind. But that's not how it works, if you're defeated on a manifesto in one election you can change the manifesto and run again, it is the logical thing to do. There's no rule which says every position must remain cast in iron and never change.
Corbyn really was a guy that just stuck to the same things forever and basically didn't move on from the 1980s. The people that criticise Starmer now, didn't like Corbyn much, and didn't like Miliband much, and didn't like Brown much (hmm ... there's a bit of a theme developing). There's a lot of different flavours of Labour there, some of them easily better than the Starmer flavour ("chaos under Ed Miliband"). All rejected at elections. The unchanging ideologue guy that supported popular policies like nationalisation (which always polls outright majorities) was Corbyn, he didn't do so well, the media demonised him and that ended him.
So what the UK is going to get is Starmer, the New Labour Atlanticist guy, a Tony Blair on steroids. He's going to bang on about immigration, being tough on crime, "making Brexit work" (lol), and basically all the Tory talking points. The crazy right wing media (most of the UK media) won't be able to attack him, because he's saying everything they are, what are they going to say "this fucking guy, he supported Corbyn, but is now as nuts as us because he knows that's how you get elected"? The Tories have fucked everything so badly, this strategy will get Starmer in, just like it got Blair in. It's not about the policies or wooing dumb voters, it's all about preventing the UK's out of control media from being able to attack him.
The Labour ad about the Tories not locking up the paedos , looks like a warning shot to me. Especially how the Labour shadow cabinet defended it. They're going to play the same game the Tories do on the same themes. Wait until they start running the immigration ads stating the Tories have opened the flood gates.
Starmer then changes nothing about how the UK economy is structured, just like Blair didn't and the UK continues to stagnate/decline. Starmer maybe does some constitutional changes because they're cheap, just like Blair did. The same complaints are then made that were made about Blair, by people that got what they voted for.