Why is accessibility a bad thing?

I've been having a debate with a former MFA colleague about this article. In it, author Joan Houlihan argues that accessibility in poetry is killing the form:

(An accessible poem) is a poem we can understand. Immediately. We feel no drive to delve. It is not a poem we need to analyze. There are no pesky layers of meaning. What you see is what you get.

Houlihan bats at poets such as Billy Collins and Ellen Bass:

In some ways, such writing is worse than that which obfuscates and fancy-dances in order to create a dazzling surface, a distraction from its basic emptiness of content or intellect. The (too-obvious) meaning in a Bass poem cannot compensate for the lack of a dazzling surface.

Houlihan can keep her academic snobbery. It's a major contributor to the sad fact that many people loathe poetry.