There's two distinct issues here.
One is running trains where only the driver has safety critical responsibility. My issue with this stems from the fact that you can only pile so much onto one person before mistakes (and I don't mean criminal negligence, like the James Street incident) are made, and these mistakes, especially in the dispatch process as we've seen with this recent incident on SouthEastern, can lead to serious injury or death to a passenger. I don't think it's fair to expect a driver of a ten coach (or whatever length train) in potentially the middle of nowhere with tens of miles between stations, having answered a passcom and found out his train is on fire, to have to balance finding a suitable stopping place, with making the necessary protection arrangements for an evacuation, with making a suitable PA announcement to try and reassure the passengers, with crew calling the onboard staff (if there are any), with going back and coordinating them to assist with the evacuation, with establishing a muster point, and the list goes on.
The second is running with no staff onboard other than the driver. From a customer service point of view, it's poor, as the proposal to run without crew in disruption is exactly when you need onboard staff. Even now, with a myriad of staff who can be called upon for assistance you still find folk who are trying to get to Sheffield heading RA Coventry. It also means you're then piling even more work onto the driver, who's now also got to set up the TMS (or equivalent), potentially make announcements, potentially end up having to walk back to put wheelchair passengers on and off, etc. The driver won't be able to go back and fix the toilets when all but one on the ten coach train have decided that because it's the third Wednesday of the month they're going to stop working, they won't be able to deal efficiently with any medical emergencies on board the train, when some wally decides to start to have a smoke in the loo they'll have to stop the train to check there isn't a fire.
It's clearly an attempt to try and run the railway with as little human input as possible, and as I mentioned on Facebook the other day, it won't be long until after they've purchased their ticket from a machine, got on a computer-controlled automatic train, following the advice of the computer controlled CIS screens and announcement, the only interaction a passenger has with a human on the railway will be when they're being reported for prosecution because they've ended up in Inverness instead of Penzance.