Most English poetry is pretty simple to understand once you know the language used to discuss it.
Take iambic pentameter, one of those cases where the name is a literal descriptor of the form.
Iamb: A metrical foot consisting of an unstressed syllable followed by a stressed syllable.
Foot: In this context, a set of syllables arranged according to a predetermined pattern. An iamb is one; a trochee is the reverse of an iamb (a stressed-unstressed pair). There's a fancy name for each possible combination of stressed and unstressed syllables. This is used for English-language verse which fixes the number of syllables and stresses (accentual-syllabic), and for quantitative meter (which doesn't matter unless you're studying Classical poetry, you poor bastard).
Pentameter: The meter in which each line has five feet.
Even outside that, English poetry often tends to be prescribed in form - take, say, the villanelle: you might have no goddamn clue how to write one, and there's actually a fair degree of specificity, but once you've learned it it's simple. Five tercets and a quatrain, plus some pairs of repeated lines.
Like most, there's a famous example to study.But yeah. English poetry is mostly just knowing the language used to discuss it and memorizing the arrangement of specific forms. The real complexity comes in having the proper artistic sense to know when and how it's appropriate to
deviate from the form; very few great poets rigorously obeyed the tenets of whatever form or meter they worked in for every single piece. Older stuff, particularly from the pre-industrial British Isles, tends to work well both read and spoken, since it was often traded around and passed on orally--there's some interesting history to be found about that, stuff like how poets would sometimes disseminate work by reading it at inns and such, where travelers would record and retell it as they traveled.
Grain of salt of course, it's been years since I read and wrote about this.
As for unrhymed free-verse, that barely even counts as poetry, don't pay attention to it.