The recent stagnation of the OS has nothing to do with attempting to maintain backwards compatibility.
I think it’s fair to question whether the decisions around backwards compatibility have been worth the cost but I’d imagine they’re already doing that. Enterprise IT departments love Windows but nobody else does, and the generation of people who grew up using iOS/Android and macOS/ChromeOS for school aren’t going to jump at the chance to bring that enterprise IT experience into their personal lives.
The file system is a great example of how Windows has evolved, actually. Windows 95 was (initially) still using FAT16! NT4 was using NTFS 1.2, we're now on NTFS 3.1. To the file system itself MS added (per Wikipedia): disk quotas, file-level encryption, sparse files, "reparse points" (dunno), journaling, "distributed link tracking" (also dunno), "the $Extend folder and its files" (ditto), and better MFT recovery. Also, apparently not part of the file system itself: symbolic links, transactions, partition shrinking, and self-healing. And that's just what I gleaned from the History section on Wikipedia's NTFS article; I'm sure there's more.
Apple specifically was much slower catching its file system up with Microsoft, despite their disinterest in backwards compatibility. And if Apple jumped ahead a little with APFS, well, NTFS holds its own just fine against APFS for 99% of users. And for when it doesn't, there's also ReFS, an entirely new next gen file system used on Windows Server, and is now slowly making its way onto the desktop.
It's the new stuff that is slow and unusable.
Now imagine if you could get rid of all that legacy crap to make it work in the first place. Microsoft CAN’T do that, because the entire premise of Windows is backwards compatability.
Apple? They don’t care. Killing 32bit apps? Just make an announcement saying that in 2 major macOS releases, macOS won’t be able to run 32 bit apps. It cuts down bloat, and it cuts down on the potential attack surfaces for malicious actors.
Obviously just about everyone would agree that Windows 1 -> 7 was progress. I don’t think you’ll find too many people who’ll say the same about Windows 7 -> 11.
What would be the consequence of this? What harm does this do? Would it be worth Spotify and Slack breaking when I upgrade my OS?
That's easy to imagine: people would have zero reason to use Windows.
AirPort Utility? Apple disbanded that team in 2016. There hadn't been a new AirPort since 2013.
