The reason you don't see many iPhone owners complaining is because they're probably ashamed that they spent the money on them and are still unhappy. I'm not an Apple hater. We own an Air (6 years and counting) that survived being dipped in champaign, a Time Capsule, an Apple TV and have bought together a total of 5 iPhones over the years.
Our phones previous to the iPhones were Nokia N900, N97, E97, N95, Samsung Galaxy Omnia, Nokia 6310i, Sony Ericsson, and some other Nokias and Siemens, but that was a decade ago or more. iPhone stability beat everything else by far when we got in at 4S. It has declined since then.
As for user culture, my wife regularily closes all apps, so as to limit their impact, she doesn't use stupid apps and doesn't play games. She learned to close apps ever since the N97.
The previous best phone before 4S was by far the N95 and the 6310i before that.
The decrease in stability over the Apple phone hardware and is versions is real. If you want hard data, please ask Apple for their support numbers ;) alternately, just check the support forums.