Figure I'll toss my $0.02 in ...
It's been a while since I owned/used an iPhone ... last one for me was a 4S. That said, the rest of my family (3 brothers and both parents) use all Apple mobile products - phones, tablets, etc. so I get to see what's up with the most current iOS devices on a regular basis.
For me, the 'problem' with iOS devices isn't the "look" of the phone (ie: lack of themes or customization of looks) ... it's the fact that you're pretty well locked down on default apps, widgets, using your phone as a mass storage device, etc. It's THOSE features that I love about android, and cannot get in a meaningful way on iOS.
I don't care about apps that are slightly more "polished" on iOS vs. Android ... As long as the apps work to do what I need them to do, I'm fine. And eventually most android apps catch up to the iOS apps - at least the ones I've been using over the years (for example: iOS skype has always had animated emojis, which is nice. Android skype did NOT up until recently. I missed the animated emojis in skype, since I use skype a lot for chats/texts ... but by no means was/is this feature enough to make me want to go back to iOS)
Anyway, I have said plenty enough before that if Apple would do a few things that I consider "small, easy changes" ... I would CONSIDER using an iPhone again ... list of changes is as follows:
1. add real widgets
2. let me place app icons on the home pages as i want, and not have them auto-arrange to fill up starting at the top left
3. add an app-drawer to hide apps you don't commonly use
4. allow me to access the excess storage on the phone, so I can drag/drop pictures, videos, music, and data files at will
5. (this goes with item #4) Stop forcing people to use iTunes to do anything other than drag pictures OFF the phone
6. Let people set a third party app as a default app
To ME, those are easy changes that do not require any changes in hardware ... just extra options in the software that could be easily implemented. Just add those in, and let the user decide if they want to use the default settings for everything, or if they want to change some things around. None of those things would seemingly affect the fluidity, efficiency, usability, etc. of the phone.
Apples mobile devices are beautiful pieces of hardware that work very well from everything I see ... they just need more options for end-users to make the phones that much more efficient on a personal level. In my best Forest Gump voice ... "That's all I have to say about that."