chucks PC out the window
There are people out there who literally get new smartphone every year. I've had the same PC since 2009 and have upgraded parts as needed. It's way more powerful than when I got it and I can actually do productive things on it. Sure there are people out there who are entirely consumers of content, but don't try to speak for everyone. There will always be a PC market unless in the future you can plug in your tiny smartphone into a monitor and literally do all the same stuff a full size PC can do.
That garbage can size box is dead. Soon to be replaced by some future version of the Surface.
What makes a producer PC, vs. a consumer tablet/smartphone, is actually the physical user interfaces. Namely, the keyboard and the big display (and accessorily, the mouse, since it's hard to keep your arms up to touch the screen).
Smartphones have displays that have the same resolution as desktop, namely 1920x1080.
The logic board of the latest MacBook is no bigger than a smartphone.
There are PC-in-a-keyboard such as the OneBoard Pro+ that include an Android system.
If you hook a bluetooth keyboard and mouse to your tablet/smartphone and project the display to a bigger screen, then you can make it a perfectly good producer computer. (granted, easier done with Android than with iOS, given the silly restrictions on software production on iOS).
Also, you may consider a 20+" desktop tablets such as the Toughpad 4K Tablet, running MS-Windows, you cannot say that you cannot produce on MS-Windows. With it, you don't need a mouse, since the tablet is flat on your desk.
No, the problem is not the hardware, is the shortsightness of Apple that restricts its system and the applications it allows on its hardware too much. There's also the problem, present both on iOS and Android (even if less in the later case), that the system restrict access to files by the applications. So it is harder to write different tools manipulating the same files on those platforms than with usual systems.