I used to be an iPhone user for many years until iPhone 5. My Android phone broke and even though I also own an iPhone 6 for testing, it was so frustrating to use that I'm using my Android tablet as a phone until I fix my actual phone.
iOS is just stupid. You have to memorize all these gestures for no reason. No discoverability, I bet most people don't know about 80% of all available gestures. To go back to the previous screen I have to press firmly, then swipe—but all the way to the right, or if I stop I trigger overview mode or whatever is called.
macOS suffers the same problem, but to a lesser extend.
Unfortunately, Johnny Hive has completely lost it. He's been obsessed with out things _look_ instead of how people are going to use them—and that's why people keep hitting his glass walls at Apple's HQ. Steve Jobs kept design at bay and insured a mix of beauty and usability. Now that he's gone you can tell that products got worse and worse in terms of usability (but 1.2 millimiters thinner, and so beautiful).
Maybe with Hives gone things will improve. The MacBook Pro 16 is a step forward (besides ports).