I agree, that always baffles me on here; Let's introduce an express service* from (South of) Leeds to Carlisle then after that send it on a really slow route to Glasgow, so that the existing circuitous XC service would actually still be quicker.
*Of course the RailUk service would still draw the punters due to having nicer seats that are window-aligned, full first class with a full English breakfast (including black pudding), be loco hauled and operate on a superior taktfahrplan timetable.
On a serious note, the Settle and Carlisle Line is moving in the right direction with having later last trains and more trains overall along with the Bentham Line. That's all that's really needed on the route for the moment.
Some more semi-fast and through services are in the nice to have category, but are far from essential.
In my experience, some of the 2 carriage services need to be longer as well.