Pilky is an Apple platform developer who writes about Mac, Xcode, AppKit, Swift and Apple's technology changes.
HN commenters cite his posts on why Apple dropped 32-bit, the overpriced Mac Pro, and AppKit's evolution against UIKit.
This post here has a section on the reasons to drop 32-bit
https://pilky.me/apples-technology-transitions/
But essentially storage and memory savings, maintainability savings and some issues with the ObjC runtime.
I assume part of the issue too is being able to enable pointer authentication, which afaik uses the higher end bits to store data, and being able to do that allows them to secure the OS better. So 32-bit support likely was a security risk factor as a result too.
The Mac Pro is grossly overpriced, thought this piece captured it well. https://pilky.me/the-mac-pro/
It’s also timed poorly because right now Ryzen is the hot new CPU, and much cheaper too! Apple are missing out, and unlike the author I think making a Ryzen Mac would be easy for Apple, Mac OS already runs on them (hackintosh).
That’s just not true. AppKit has evolved a lot since 10.6. Big changes in Lion and lots of incremental improvement since.
UIKit may be more modern in some specific aspects, but it’s also far more limited. Here’s a good post highlighting some of the most obvious differences:
https://pilky.me/appreciating-appkit-part-1/
https://pilky.me/apples-technology-transitions/
Section "Why Drop 32 Bit?" (last quarter of the article).