Literary criticism is only important in teaching literature if the teacher wants to know what he/she is talking about. If one doesn't want to understand the literature and then be able to teach what one knows to others, then by all means one doesn't need to study criticism.
Also, your question doesn't ask about literary theory, it asks about literary criticism. Criticism is any analysis of literature. When you do a close reading of a text, you are performing literary criticism. And the more close readings performed by others you read, the more you will know about a text. You shouldn't blindly accept everything you read, but you should read everything just the same.
Furthermore, just in case you had theories in mind, such as Feminist, Economic, etc., those, too, are vital. Every approach applied to a text that you study has the potential of teaching you something you didn't previously know. What could be more important than that?