My father was a professor of literature and I am reasonably confident that if he were asked this question he would say that the purpose of criticism is not to figure out what the author meant, but to fully understand and appreciate the nature of the experience that the work creates.
He spent much of his career arguing for the superiority of the 1850 version of Wordsworth's prelude over the 1805. The 1805 version is considerably more liberal in its sentiments and it was preferred by many of the scholars of the day for that reason -- they considered it to be a better work because it expressed more liberal sentiments compared to the more conservative sentiments of the 1850 version.
But my father's argument was not that the 1850 version was better because its politics were more conservative, but that it was better because it was better poetry; that its images were more striking and its emotions both more mature and more deeply felt. (I'm paraphrasing his argument wildly, but that seems to me, through the filter of memory, to be the gist of it.)
I also remember an anecdote about Beethoven which I assume I must have heard from him. A woman came up to Beethoven after a concert and asked him what the piece he had just played meant. Beethoven answered by sitting down at the piano and playing it again.
A piece of art, in other words, means itself, the totality of its experience, and nothing else. The purpose of criticism is both to judge the quality of the experience as an experience and to make the fullness of the experience more accessible to the reader.
Of course, this is not the majority view among literary critics.
But to me, the notion of a piece of literature as a covert polemic seems odious. I believe that a writer turns to fiction not to conceal an argument which they are very capable of making plainly, but to record an experience. Sometimes, in other words, what you want to say is not that the world should be such and such, but simply that the world is such and such, not how human life should be lived, but simply what the nature of human experience actually is. Experience, by its nature, cannot be conveyed in summary. It can only be taken whole. The meaning of a poem is the poem. The meaning of a novel is the novel.