Intricate gestures are difficult to grok for some, and difficult to perform for others. Try using an iPhone and closing an app with shaky hands.
Currently the iPhone SE still has a physical button, but I'm worried what device I'll start recommending to older/less tech savvy people when that goes away.
iOS itself is a bit of a disaster zone too now. I see people constantly get stuck having activated the "press to edit your lock screen" by mistake, or getting confused by a constant stream of ads for iCloud, Apple Arcade etc.
It's sad because most of this poor UX is unnecessary. It feels like its origins are in Apple no longer caring, combined with running out of real ideas and getting distracted with things like widgets.