Poetry is often very critical of the culture from which it emerges. Quite often literary critics of a nationalist bent talk up the national culture, in a way that the literary texts don't. Poetry can bring out areas of denial and repression.
I think that literature quite often emerges from areas where there has been a lack of articulation, like women's writing.
Obviously all writers, all artists, have their own internal critics; as they write they are being self-critical.