There is nothing at all about the Calibre interface that needs to be the way it is. What's so interesting is the way it apes an old version of iTunes, one which nobody would've considered the pinnacle of UX, and still manages to complicate and bury things in unexpected places.
There are well-documented user interface design guidelines to follow, both vendor specific and general ones made by experts like Jakob Nielsen.
Well-designed user interfaces lend themselves to user experiences where the learning curve is low, not steep, sometimes coming close to flat.
The only excuse I can fathom for those who prefer the learning curve be as high as possible or never be lowered is resentment that their own efforts to scale the same mountain of learning the UI themselves.
I call that technical elitism. It says “I worked hard to learn how complicated interfaces work, everybody else should be held to the same expectation”. No, they should not.
1. I can't figure out how to change the styling of the book viewer. 2. Whenever I search, then try to hit backspace to modify my search terms, it tries to delete the first search result.
I find Calibre is not a tool to "enjoy" spending time on, but simply a tool to solve something specific so that I can then spend time on my Kindle.
There are other tools where I want to enjoy the time I spend using them (say, text editors, paint programs, IDEs) but Calibre is not one of them.
No, it doesn't. Eventually people learn to use it, and everyone is happy that way.