I know that doing random shit on my phone during my commute absolutely fries my attention span, but I don't have any solution.
Try it - I find that I get most engrossed in a book on the Tube. Main problem is the risk of missing your stop
Plus who knows what those people were doing on their phones - sure some people are just watching netflix or whatever, but I have seen many people doing things like learning languages or learning to play piano etc: things that most people would say are laudable pursuits and which would not have been possible without phones.
Imagine for a moment that we don't use our hands to use a device: you wake up one morning, board a train and everyone has a head-harness holding a rectangle in front of their eyes. It’s a very strange sight. But I’m old and my days are numbered; this isn’t my world.
What's wrong with people being on their phone though? I barely use my phone, but if I'm in a tunnel and there is nowhere to look, yeah, I'll read a book, online news or email. I rarely socialize on the subway and I have one of those glances that make people uncomfortable.
Anecdotally: I just came back from London. Big fan of the new Elizabeth line. The Piccadilly (and most lines) low ceilings are a bit soul crushing (I'm tall, but I suspect for most people too), although I really like the character of the old stations.
I imagine that if she had a phone, or I was staring at mine, that would never have happened.