The blank-slate protagonist of Murakami's novels works pretty well. The aimlessness, lack of connection to the world, even his mediocrity, make him available to what is proposed to him. He has negative capability. Someone with more of a definite personality would not work as well. He has to be free (left by his wife, un- or under-employed), a bit stoic. It doesn't matter that it is the same generic character in several different novels. A reader (male at least) can identify with him as an everyman.
Of course, he has to be strong too, resilient when things start to happen. Mediocre everyman has to rise to the occasion. The modesty has a power of its own. It doesn't even matter that many of the other characters are more interesting than the protagonist. He doesn't have to be interesting because things happen to him.
The banality of the original anecdote of Queneau's stylistic exercises is similar. A story with more inherent interest would not work, because the key is the stylistic variation.