A few random thoughts...
I think a lot of people forget that the Johnson government is just as left wing in many ways as New Labour was. This isn't David Cameron's party of austerity. Boris Johnson is a believer in big government, state intervention and the magic money tree.
My personal belief is that he isn't fit to lead a government, yet lots of people adore him. I know a scarily large number of 'working class' people (pensioners, people on the dole, shop workers and similar) who voted Conservative in 2019 because of him when he, in reality, knows little and cares even less about them. Until Labour manages to understand the appeal of Boris Johnson, I think they'll continue to really struggle.
In Hartlepool, if Labour lose, some people will blame Corbyn, some Starmer, and some will say Johnson is too good. However, the figures speak for themselves. The rot set-in when New Labour were in government. Since 2010, they no longer weight the Labour vote in northern seats, but actually have to count it. During the 80s, Labour consistently got 20k votes or more in the seat. This continued until the 2001 election. After 2001, the New Labour rot then began - yes, Labour still held the seat fairly safely, but the raw Labour vote just fell and fell. 2005, 2010, 2015 and 2019 were all elections where Labour won the seat, but struggled with votes. 2017 was actually a pretty decent election for Labour where they got over 20k. Corbyn obviously wasn't hated too much back then and May was a much easier opponent with her disastrous campaign. By 2019, Corbyn's image was soured in the public's mind, Labour's campaign smacked of desperation and the Conservatives were now led by Johnson.