I don't doubt that commuter traffic is down in the SE. The three franchises that operate south of the river were always pretty inefficient, they'd be packed for a couple of hours in the peaks but for the rest of the day there would be sidings full of spare trains with others rattling around empty.
What I fail to see is why we in the North should have to put up with service cutbacks just because no one is commuting in the South. I stand at Crewe and continually hear the auto announcements saying "this train is expected to be very busy, passengers with flexible tickets may wish to use a different service" on every train to London. Likewise TPE would have more passengers if they could be relied upon to turn up - it's not uncommon for only three of their fifteen Cleethorpes trains to actually run on some days, leaving passengers travelling between Manchester and Sheffield to join a Northern stopper. How many people are claiming refunds as a result of their inability to run a service? The remaining TPE trains aren't exactly quiet anyway, five car 802s have replaced three car 185s but they're still often full.
The demand here is consistently spread throughout the day, all week - trains carrying commuters into Manchester depart full of holidaymakers going to the coast, return with the holidaymakers on their way back and finally work the evening rush hour. Pretty efficient as those trains are full for most of the day. In fact they often leave people behind, such is the demand, I've had scores of passengers stuck at stations for several hours because train after train is too full to squeeze anyone else on. Before the pandemic I remember working a train on an race day and giving up trying to squeeze through and collect revenue, I worked the very same train earlier this year and despite having double the number of coaches I had to give up ticket checking at exactly the same point in the journey.
Even on commuter runs, on many days we're seeing much the same loadings as before the pandemic.
What would really help is better revenue collection. Half of Liverpool Lime Street is unbarriered, to the extent that the residents of Runcorn refer to Avanti services as "the free train". I've taken forty fares on a single departure from Lime Street on a Saturday night. Almost all of whom must have travelled there earlier and avoided being checked. It's chronic at Warrington too, and presumably Wigan NW. They installed barriers at three of our stations about 15 years back, estimating that they'd recoup the outlay in two years. No. Two of the stations recovered it in three months, the other only took one month to pay for the investment - they'd underestimated the problem by a factor of 24.
Perhaps if the government actually tried to be constructive in the way it runs the railway, these negotiations may be different - electrification schemes, installing ticket barriers etc. If you try to balance the books just by cutting costs, you will eventually cut yourself out of business. You need to look at growing revenue at the same time.