When dealing with an enormous topic such as poetry, it does help to narrow the field to a specific area. However, a responsible writer indicates that as a process, rather than acting as if the rest of the material doesn't exist.

So for instance, a poem can matter on an internal or external basis, individual or localized or very widespread scale, and so forth. Different types of poetry have different purposes. If a depressed person finds writing poetry to help express buried feelings, then it certainly matters to them -- even if nobody else ever reads it. But that's a whole different approach than poetry meant to move large groups of people.