This thread correctly identifies "discoverability", perhaps aka "progressive disclosure", or "some form of incrementalism" as the measure by which good user interfaces are evaluated. Operating systems such as Windows, OSX, and Linux -- inevitability -- contain much complexity, and multiple modules, not all of which are necessarily in use by the users at any given time.

Therefore, the problem of GUI design becomes one of navigating the complexity/depth-of-knowledge curve, as much as it does creating a usable set of features at each point along it.

The most egregious offenders are the latest Windows, 10 and later, IMHO. When I was a kid, (coming from the world of RISC OS which had a much shallower GUI) trying to understand the big deep Windows interface, I joined the dots by telling myself "This is how they put it together. This is how they are trying to make the things work consistently and in concert." I rarely broke out of that story-telling loop.

Now, when using Windows 10 or later, and a few clicks brings one to a Windows 2000 and before-era network dialogue box, the "fourth wall" as it were, of GUI design is broken, the story-telling loop above is replaced by a jarring feeling of bewilderment or all-too familiar frustration, and it's obvious they are shipping the org chart, and doing so over time, as much older GUI components are still available.

At the risk of sounding nihilistic, I fear that both OS X and Windows have reached their respective local maximas of design, and we won't see any changes for the better (by the above metric) any time soon.