That might not be a bad thing. I've used Android for a while, but I'm not always clear if/when the back button will do in-app navigation vs. return me to the phone's home screen.
I've always regarded the back button as the single most important reason why I prefer Android to iOS. Interesting how different people perceive the world.
I agree. The back button in Android almost always seems to do what I would expect. I'm not an iOS user so my perspective probably doesn't mean a lot, but the occasional times I try to use someone else's iOS phone I have no idea what's going on. Nothing seems intuitive.
iOS's Swipe From Left works differently than Android's (at least 8.1 Oreo's) does, but often accomplishes the same task. It's pretty equivalent to Android's back button in a lot of cases, acting as hierarchical navigation and back to previous screen when applicable. The difference is that it only works within an app, which means it won't kick you back to a previous app (unless it's opened in a web view) and won't take you back to the home screen. I typically found iOS to handle it more elegantly than my <=Android8.1 phone, but I haven't updated to Pie yet to see how it's different.
Because Android features this metaphor, it's used extensively. Because iOS doesn't, it isn't as much. iOS features different metaphors which achieve the same outcomes in different ways, such as pop-up sheets for the camera, album views and share panes.
And in cases where one app does activate another, you can go back one step by tapping the top-left corner of the screen. There's only one level of "app back", but that's plenty since iOS doesn't tend to jump you between apps a lot, and because that navigation isn't co-mingled with other "back" operations.
