The alternative view is that it is making the railway less complicated, more ordered, and more efficient because there is a set way any journey is made with the same times each hour and same connection point.
But losing circa 80% of through passengers in the process. Arup engineering did a detailed study into this and every introduced connection loses circa 80% of passengers. Taken to its logical conclusion, why not run every service between just a station pair and introduce more connections in a more ordered and efficient way - and discourage everyone from travelling in the process?
Customers want direct services, not convoluted journeys with connections. Just the idea of missing a connection is enough to put off lots of people.
In what way was a train at 1632 from St Pancras leaving Sheffield for Leeds around 7pm a good use of resources? It admittedly ran in marginal time but will have only been useful to a small number of potential passengers and from Derby northwards just duplicated the Cross Country service.
I think you have a thorough misunderstanding of the communities this service connected. It was the only service of the day connecting Leicester and North of Sheffield, as well as Loughborough and East Midlands Parkway. In some cases, this takes 2 connections down to zero. It also provides an additional useful link from Birmingham (departing circa 1700) towards Wakefield and Leeds, duplicating the cross country service, with one of your highly advocated connections.
It's a perfectly decent use of resource, as in the current timetable, the set simply runs to Sheffield and then ECS to Etches Park. Previously it ran in service to Leeds and in service back to Derby, being reasonably well used in the down direction.
The withdrawal of the GWR trains to Brighton gives Southern a free hand to implement its own services over that route without needing to accommodate an off pattern service.
Are you unaware that the industry does communicate? If southern were in great need to move one of these handful of trains, a simple email to GWR train planning would likely have been sufficient, as broadly the industry tries to work together.
The process of removing these awkward services will in time be seen to be advantageous to passengers with a leaner, less anomalous railway operation.
Or a less connected, more awkward railway that discourages new customer flows and doubles down on a handful of revenue flows to the disadvantage of a broader public.