I'm not much of a poet — the only poems I've made that where worth reading had no structure whatsoever — but I think I know enough to understand why
I don't get it. So:
Poetry is all about freedom of expression, right?
Ahahaha — no. You're thinking Freeverse, maybe even the ethos behind a lot of modern stuff, but that's hardly all there is to poetry. Look up sonnets, or limericks, or even haikus. If you need more rules, look for the forms that have them.
Poetry doesn't have to rhyme. I get that. But sometimes I'll see poems that are indented to the left, then center, then the left, then the right. What. The. Fuck.
What purpose is that? How does that help get your point across? Why do people prefer poems that rhyme anyways? Am I stupid for not understanding poems that seem to make no sense to me at all, using stream of consciousness to create the equivalent to literary abstract art?
I always understood poetry as having historically came out of music. It has patterns, repeating sounds (such as rhyming) and rhythms, which gives it a lyrical quality without anyone actually having to sing. It's weird, but when done right it can give a nice underpinning to the words.
Then, some time in the last century, it started getting all weird and, well, "abstract". Like in literature and art, they sort of had a forceful movement focused on dissolution of the rules, and started experimenting with things like how the poem looked on paper, or breaking meter, or not even using words at all. Sometimes the rule breaking was done for a reason, sometimes rules where broken just because they could be. Hell, sometimes no one knew there was rules. If you're not in the know, it's hard to tell the difference.
I think the most important thing for you to do is start simple and learn all the jargon. They're playing speed chess, you're trying to figure out what the hell a rook is — referencing them while you're learning is only going to confuse the hell out of you, especially if they aren't even playing with rooks. Settle for trying to figure out what the basic structures behind poetry are, like meter. Go on the Other Wiki
and Wiki Walk
your way around from there.
Also, try to find poems and poets you actually like, so you can slowly start to figure out what you want out of your own stuff. At the very least, learning will be a bit more inspiring that way.