>Depends on what you mean by “accessibility”… my 85-year-old aunt-in-law finds her iPhone 7 running iOS 15 to be far less accessible than her old iPhone 4 that probably stopped being updatable around iOS 7.

Yes, I've heard the exact same thing from my iPhone-using elderly mother and my sister. The answer is simple: stop spending thousands on new iPhones, and get an inexpensive budget-model Android instead. They're quite simple to use. But my suggestions always fall on deaf ears.