> The sad truth is that the status quo for GUIs is absolutely terrible, and most were rushed out and not properly tested to check if they're really usable without a mouse.
This is the key point. No platform UI paradigm focuses on keyboard navigability and speed, all focus on mouse and visual effects for discoverability in a pursuit to dumb down the user experience enough to make it usable for everyone, breaking power users in the process (and increasingly also accessibility stacks).
I think the real problem is as computers have become more mainstream, they've become more subject to whims of fashion. Consumer-focused companies don't want to be seen wearing last season's UI paradigm. Just watch Apple change things around...
This is the key point. No platform UI paradigm focuses on keyboard navigability and speed, all focus on mouse and visual effects for discoverability in a pursuit to dumb down the user experience enough to make it usable for everyone, breaking power users in the process (and increasingly also accessibility stacks).