As a, mostly, happy Android user since the HTC Magic in 2010 or 2009, the one thing I really wish they could fix (but I suspect it would never be possible) is the extremely confusing thing with intents and apps opening as views in other apps. Like when my mail app opens a PDF it looks like I am now in the PDF app and after reading for a while I completely forget that I am actually still in the mail app, and then I go BACK and instead of ending up in my PDF library view as I expected I am suddenly in my mail app. Or when I look at the running apps list there can sometimes look like I have two PDF viewers or two browsers running since some other apps used intents to open views from those apps that now exist in parallel with the real apps.

Somehow that manages to surprise and confuse me almost every day. In desktop operating systems, and, I belive, in iOS, there is no need for such thing? Opening a PDF from a mail application usually just opens the PDF viewer as its own application, or it is embedded in some nice way that does not make the entire mail app suddenly look like a PDF viewer app instead.

Unfortunately they can probably never fix that because app lifecycle and intents are connected to everything and a good fix for this would probably break everything.

It's interesting that this feels awkward to you, because when apps don't function this way it feels broken and odd to me. When I tap a PDF attachment in an email I expect the back button to go back to the email I was just viewing, not the list of PDFs on my phone. If I wanted to view all the PDFs on my device, I would start at the PDF viewer and tap into PDFs from there.

I wonder what experience made this feel more awkward for you (and conversely, why it feels more natural for me). What a weird/complex world we live in!