How can we evaluate poetry?

Recently I had the fortune to read a few poems written by a friend of a friend, and I'd like to share part of my response to them.

Dear A––––––, 

After I read a few of your poems, I asked Kate what she thought about poetry in general. She never reads it, and I was curious. She said she has a hard time "evaluating" poetry–deciding on whether it's good or naught.  

More or less, I told her, "I think there are two kinds of poetry: Poetry with an apparent structure and intent, and poetry whose structure eludes us. 

"When we see a poem that has an evident form–quatrain, villanelle or what have you–we can evaluate it on its adherence to the form, it's capacity to achieve an effect within the confines of that form, it's originality, etc.

"However, when the poem doesn't have a clear, visible form or structure, we can still evaluate its ability to achieve an effect, but that's where the evaluation has to stop. 

"If we can't make sense of what the poem's intent is, we can't evaluate it's effectiveness. And since it takes no effort to compose gibberish or empty, meaningless language, and therefore no originality, we can't judge the poem on it's originality if there is no apparent structure to the words. Thereby, the only thing I can think of on which to evaluate such a poem is it's ability to make an effect upon us. And that is highly subjective. Arguably, a quality so highly subjective as to be not worth pursuing.

"I don't want you to take away the impression that only structured poems are worth reading. Not at all. Nor do agree with the idea that poems which don't have an apparent intent are de facto void of value.  I won't say that, but I will say that for the purposes of evaluating a poem, the concept of evaluation is only meaningful when there are clear criteria, or standards, against which the poem can be evaluated. Sans any reference point, the quality or "value" of a poem without apparent structure or form is dependent upon the reader. 

"Question: What is it worth? "Answer: What is it worth to you?"

 What do you think? Comment below.