TBH, I'd have Momentum as well up the list of least influential party groupings ever. This has them with 35,000 members in 2018 - and the dominant voice in something like a 350,000 rise in Labour membership:
Momentum surges past 35,000 members with ‘more than 1,000 members joining every month’ | The Independent | The Independent
Didn't manage to reverse Labour's disconnection with working class communities and didn't even get a grip on the party itself.
I'm using Momentum as shorthand for Corbyn supporters. I joined the Labour Party for Corbyn but never formally joined Momentum. Labour membership swelled dramatically during that time, and it has now shrunk just as dramatically under Starmer.
They didn't reverse the disconnection, but as you say they failed to really get a grip on the party itself. And that's my point - the LP has proved that it cannot be redeemed, and so it is no longer a viable political party. As soon as a credible left alternative emerges, Labour is doomed. See - SNP in Scotland.
New Labour's political gambit was that they didn't need to worry about the working class or the left as they had nowhere to go, so they should focus on the middle class and homeowners. By 2010 this was already wearing thin as appealing to homeowners ignored the rising numbers of younger people priced out of home ownership, and at the same time the foundation of community loyalty to Labour was naturally withering with the decline of organised Labour.
The Corbyn project was an alliance of Old Labour (Corbyn, McDonnell et al) and the children of traditional Labour voters to ressurect the old party. It failed, but it also kept the moribund Labour Party alive longer than its natural lifespan. The Corbynista activism and vote wouldn't have gone to Labour otherwise, it would have found/created a new outlet and Labour would have gone the way of the French Socialist Party or PASOK by now.
By stamping out Corbynism, the Labour Party have signed their own death warrant.
There is a huge class issue which overlaps a great deal with age, and that is property ownership vs tenancy. Corbyn got the youth vote because he actually acknowledged that tenants exist and tried to address their interests, which to me was exhilarating as in alI my life I had never seen a politician do that before. Tbh I think this was the primary driver behind his support. With trade unionism insignificant among the younger generation, the only material way for Labour to generate loyalty among a new generation was to be a voice of the growing tenant class. By doing this, Corbyn breathed new life into Labour.
However, the PLP throttled this new life as soon as they got the chance and rushed to return to a policy of sucking up to the propertied and pretending tenants don't exist. In doing so, Starmer's Labour has removed any possibility for Labour to survive by terminating the foundation of youth support, and residual support out of tradition which they have been coasting on since the 90s is fading with time.
There is no longer any basis for voting Labour, but social democratic (in a broad sense) ideas remain strong and it is only a matter of time before someone pulls the rug out from under Labour. NIP could be the ones to do it.
And yes, those of you who were saying the Labour Party is a waste of time were correct. But it was still worth a try, and it didn't feel like there was any tangible alternative being offered that I could contribute to or get involved in.