the OP is talking about the Northern-only promotion which is at a bargain price but comes with corresponding limitations
Agreed - it's a discounted ticket that offers less than a full regional "Rover" and costs less than a full regional "Rover" - it wouldn't exist under a "nationalised" railway, so seems a bit strange that it's being criticised like it is here.
As the line from Newcastle to York can have
- 2x LNER (possibly increasing to a third if the proposed Sunderland/Middlesbrough services are introduced)
- 3x TPE (two to Newcastle, one to Middlesbrough)
- 2x XC
- ?x Freight (there may only be a handful of freight services but that may still be sufficient to block out a clockface path for other TOCs, especially given the speed differential between freight and InterCity services)
- 0.5x GC (branching off for Teesside)
...so I don't know where the room is for a "regional" DMU service pathed at 75mph.
The current Northern service through Durham only really runs because the InterCity depots in Newcastle/ Leeds/ London etc mean there are gaps in the morning peak from Darlington/ Durham into Newcastle (since most units are leaving Heaton in the morning and it takes a while for the units from Neville Hill/ Bounds Green etc to be arriving into Tyneside).
Maybe there's an argument that in an ideal world, Northern would be using their DMUs to attend to demand from Hartlepool/ Sunderland into Newcastle in the rush hour, rather than diverting them via Darlington/ Durham to fill a gap that LNER/TPE/XC leave? Rather than complaining about Northern not serving Durham fully, we could say that Durham isn't Northern's problem to solve (and they could be 06:58/07:58/08:58 arrivals into Newcastle from Hartlepool/ Sunderland - i.e. proper Northern stations, instead of diverting them away from the coast because other TOCs aren't running sufficient services through Durham)?
Rather than worrying about running a Northern service down the ECML to York (to tick a box), maybe the question should be whether the "Heaton" bits of Northern could work as a stand alone franchise? Northern is already fairly messy, the NE bit is pretty independent (other than maintaining some Pacers for Sheffield - an arrangement that may change when the 142s leave), it might be a nice size for a regional stand-alone franchise (instead of being far down the list of the current franchise that prioritises Manchester and Leeds above everywhere else).