Northern needs new vehicles now. West Yorks, lancashire and Gt manc need longer trains. too many short trains entering the hubs.
I agree, although I'd go further and say that probably every TOC could do with more trains.
However that's generally happening, as according to the latest long term rolling stock strategy (2018):
The number of new vehicles committed for delivery in the five-year period that commenced in April 2014 (CP5) and in the early years of CP6 is now 7,187 – more than 50% of the current in-service fleet of 14,025. These new vehicles have a capital cost of more than £13 billion, and around 50% will be built in Britain. The average age of the national fleet is estimated to fall from 21 years to 15 years by March 2021, while the numbers of vehicles in service will grow by 6% next year and by a further 5% to 13% by 2024.
However even then there comes a point where there's no more space for extra coaches (see the £800 million invested at Waterloo to allow 10 rather than 8 coach trains to run). Without HS2 you would have to invest a lot at Manchester, Leeds, etc. whilst with HS2 this money is being provided by HS2. Chances are without HS2 you'd need to invest (say) £5bn-£10bn in stations and extra track in the North to gain the same sort of extra paths and stations which HS2 would provide as well as the basis for building NPR.
If you add those sorts of costs to NPR and it would significantly reduce the value of that project, possibly to the extent that it's not viable. Load the risk to HS2 and NPR keeps its good business case.
Bin HS2 and you risk losing NPR as well.