I really hate that the basic cost for participation has gone up, a smartphone and quality internet (in the USA) can be a significant cost.
But I've never had a problem with a screen capture of a boarding pass, and I've found the Apple wallet to work as well. The airport kiosks are good for printing out the pass when you check in, or even for just printing if you checked in on-line 24 hours prior.
I usually print a boarding pass at the airport kiosk — I always have luggage to check anyway, and there's then no concern if my battery dies etc.
But at the automatic gates to security, and at the boarding gate, I think the majority of people having trouble scanning their boarding pass are using a phone. For those elderly people who can't scan a paper boarding pass, the staff can immediately help — but they're much less able to help scan a barcode on a phone, which might be set too dim, be turning to landscape mode, etc.
But I've never had a problem with a screen capture of a boarding pass, and I've found the Apple wallet to work as well. The airport kiosks are good for printing out the pass when you check in, or even for just printing if you checked in on-line 24 hours prior.