First of all, the quote begins by invoking authority, in this case a dictionary: "The definition of insanity"--and of course the prototypical authority Einstein

First of all, the quote begins by invoking authority, in this case a dictionary: "The definition of insanity"--and of course the prototypical authority Einstein has been attached to it as well. So the quote is trying to "nail down" insanity rather than irrationality which is a much more challenging task. And you have to admit that there is a certain unchanging sameness that accompanies a typically insane person, who refuses to update his understanding of reality, his strategy of action, in response to external feedback. Thus, you tend to get the same sorts of actions repeatedly from insane people. For instance, a person who compulsively washes his hands might expect to achieve health or some other tangible benefit, when the fact is that by and large he is just wasting his time. By invoking the quote, one is able to root out insanity in himself and others by finding examples of unchanging behavior which is often connected to an unchanging viewpoint. Your complaint seems to be that this bit of wisdom misses the failure of people to update their world views, but 1) that is exactly what the quote tries to do, and 2) your examples of "same thing"/"same results" are tangential to the point of this quote. Sure, we need a proverb to encourage people to update their worldviews, even when things are working for them, but we don't need a proverb that covers all the bases. Might I suggest "The only constant is change", another wonderfully misattributed quote?