> For reasons I don't totally understand, the platform vendors are themselves constantly invalidating the information in users' heads, so there's simply less in there for application developers to build on anyway.
To be honest, I'm not sure this is true. macOS has had pretty much 1 major redesign in recent memory (Big Sur), and even that is mostly a visual update -- functionality is all still there and works the same. Toolbar buttons are still toolbar buttons, you can still drag and drop them around, etc etc. In practice, the amount that actually "churned" is pretty small.
To be honest, I'm not sure this is true. macOS has had pretty much 1 major redesign in recent memory (Big Sur), and even that is mostly a visual update -- functionality is all still there and works the same. Toolbar buttons are still toolbar buttons, you can still drag and drop them around, etc etc. In practice, the amount that actually "churned" is pretty small.