I would say it's more like this: a mouse is good for letting a user access features whose parameters they do not know off the top of their head. It allows the UI to act as a feedback loop between the human and the computer so that the human can incrementally guide the computer to do what they want. A command line is more effective when the user knows exactly what they want done and can recall immediately how to do it.
"Not knowing the parameters" can come in two main forms. The first is when the user simply may not have used the feature enough to be able to instantly recall all of the parameters needed and how they should be set. For example, a print dialog displays three or four commonly tweaked parameters to a user, and gives easy access to as many as several dozen more advanced parameters. This is far more useful than a CLI would be, except perhaps to a very small minority of users.
The other form is when you may know what the parameters are, but need feedback to choose them correctly. For example, resizing a window is well-suited to a mouse. Obviously you know that the four parameters are the height and width of the window, but few people can glance at their screen and say "Oh, I need this window to be 348 pixels wide now".
Could you explain what you mean? Seems to me that the mouse is best at expressing nouns - well, the things you see on screen...I'm obviously misunderstanding.
Why is everybody always black and white about everything?
Regular human language is multimodal, with words, explicit gestures like pointing, and body language layered over both of these (Though most geeks are deaf when it comes to the latter).
Which is easier, "Look at that [finger pointing at target]" or "Look at that strange thing on your 2 o'clock"? We have many options and we use what's best in each circumstance.
It maybe iconic, however, it's a horrible device for pointing from the point of health and ergonomics. And even with all the improvements, I've never seen a mouse handled more accurately than a proper trackball (see Logitech M570). Of course, that depends on the user.
It sounds extreme, by I personally believe that mice destroy the wrists of programmers - that's one of the reasons why we love programs and interfaces with tons of keyboard shortcuts - along with being faster, it's easier on the wrists.
In addition, good keyboard controls can make or break many programs. If you take a look at a program in the adobe suite, you'll normally notice two things. First, that using the program with the mouse generally involves awkward mouse manoeuvrings. However, keyboard shortcuts can eliminate 90% of this.
Third, do you personally recommend using a trackball? I've been experiencing some mild wrist pain lately and am looking for something better than a mouse.