Only the really major ones like Birmingham New Street, London Euston and Glasgow Central are Network Rail managed. Smaller stations with just as many operators are TOC managed. The 7 of the 10 worst stations refers to managed stations.
I think to put it simply, it was not a franchise commitment for VT to upgrade stations, the investment was all about trains and journey times.
Later franchises tended to have some station investment included.
Also in the WCRM debacle the optional bits were cut back (eg rebuilding Watford Jn).
Crewe has been in planning blight for years waiting for a decision on relocation, but at least it now has a new roof.
There are indeed some grim VT stations, but others have done reasonably well. They invested in car parks for instance.
Many stations have recently had "a new bit on the side" added (eg Stockport, Warrington BQ, Stoke) while the main buildings are unchanged.
It's a paradox that VT's flagship stations are mostly run by Network Rail.
I guess Preston is the largest managed by VT itself, and that is quite a nice station to be in although now in need of upgrade.
Other TOCs stations like Exeter St Davids and Colchester have been neglected by their TOCs just as much.
I should think the new WC franchisee will be putting a priority on station upgrades.