They re-write many apps every few years as part of their major design changes. These re-writes inevitably introduce lots of little bugs in uncommon workflows, and they often jettison whole features like AppleScript integration that cause real problems with users. They then spend a couple of years fixing the worst of these bugs, and things die down. Until the next UI-driven re-write.

Because there are so many bugs that it makes me wonder if Apple Execs ever use their own software.

For example, on MacOS, you can set an app to be on all spaces. But on reboot, despite that setting, it will stick to a single space, until you relaunch the app. It has been this way for 4-5 major OS versions.

There are PLENTY of examples just like that.

It's all been downhill since snow leopard IMO. Maybe I've just become cynical and jaded over the years, but I don't remember the last time I was excited for a new OS feature. Meanwhile the UX gets worse and worse with every new release. e.g. Tahoes janky corners, the dumbed down System Preferences app, random bugs that apple hasn't fixed for years, etc

You've not read about or had the Calculator memory leaks on macOS Tahoe, have you?

Their presumed lack of regression testing.

When was the last time you used the clusterf* that is iTunes on windows?

Or more generically answer the question: how can I get an arbitrary audio file into my iTunes music? (hint: good luck)

Music 'synced' with iTunes but not appearing on my other devices? There must be some kind of arbitrary difference between 'synced with iTunes' and 'synced with iCloud'. I guarantee this is some kind of (barely) maintained legacy syncing to keep the iTunes workflow alive specifically so Apple can avoid giving users a modern 'import to my cloud library' feature.