But if they want to teach literature, and how to appreciate it, how to identify the ‘good’ from the ‘bad’ — in other words, what’s worth spending time with and what isn’t — if they want to convey lessons on how to assess, compare and rank the merit of literary work, which I think is the most valuable aspect of studying literature. putting words to feelings…then I think it is their duty to pass aesthetic judgment, and to explain in detail how and why they came to pass it. 

As to literary merit being beside the point…well, again, in studying the political or cultural or linguistic context of a work, then no, merit may not be relevant, but if you approach literature from the perspective of the intention with which it is primarily written [and yes, I know there is a long tiresome debate surrounding this]  ( to entertain, to convey life lessons, different perspectives etc), and given limited time, are looking for the best way to spend it, then merit is at the very centre of the point.

Maitresse, I agree with you, Barthes is always interesting, and Foucault on ‘power’  structures is fascinating…esp on Madness and how the medical establishment took over the defining and categorizing of mental illness from the clergy…the point though is that good literary critics must pass aesthetic judgment, establish relative literary merit: to do this they can’t be captive to any theory. They might wish to point out a particulary strong Marxist reading for example…or identify how such readings have influenced other writers and critics but this should always be done in the sunlight.