Criticism, really, is never as hard to write as poetry, fiction or drama for the simple reason that the heavy lifting has been done for the critics by the creative authors under scrutiny. I concede that good criticism, interesting criticism, intriguing rants can entail a good amount of head scratching, research and critical thinking, but critics and other varieties of opinion-givers are building on what is already in place,the creative work. And what was there to begin with, though influenced, of course, by tradition, formalized training, influences of previous generations of bards, novelists and playwrights, are nonetheless created from scratch by the individual writer; in any sense it is more difficult to put together an imaginative work of writing from nearly nothing at all .
Criticism, even if artful, thoughtful, full of intriguing digressions, asides , sidebars and made magnificent by brilliant conclusions, is ,at base level, remarks, brief or extended, on the creative work that was in the public sphere prior to the commentary.
Criticism is not equal to the art itself--unlike Art (taken as a general concern), criticism cannot exist by itself,in itself, for its own sake. I do think criticism can be artful,memorable, important, can actually be an expressive medium on its own terms, but it remains secondary to the actual work. Like the artists,though, I would give the critic the right to respond to a work of art, something that has been created and entered into the marketplace , in nearly any manner he or she chooses and would encourage the critic to be as subjective as they can be.
Criticism is not an "objective" form, and insisting that it is only perpetuates a mythology. The critic , the most interesting critic, I think, is someone who comes to a field knowing something about the form, has a good working knowledge of the broader field surrounding the issue-- aesthetics, theory, history of form and what then current ideas might have helped shaped ideas of what constitutes art--and is able to present their preferences and biases and contradictions and exceptions in a manner that is conversational, intense, thoroughly in love in with ideas as to how poems could/should/can effectively express experience and convey perception.
The only thing the critic needs to do is to present his or her case , yay or nay, in the best, clearest voice they can muster, with no sacrifice in personality. Personality , in the hands of a good writer, is style and style is the majority reason why I read certain writers, whether poets or essayists, and pass up others.