Chalk it up to the Modernists, if you like; I tend to point the finger at Yeats because he made language a religious experience, but the esoteric poetic has lost little of its prestige in recent decades.
The result of this shift has been a homogenization of lyric, a messy divorce from readers, and an explosion of crossword puzzles posing as poems. And still, ask a poet to define poetry, and almost uniformly they will begin by ruminating on the distillation of language and the righteousness of every word. The pompousness of this definition is infectious: young poet logophiles pour out erudite absurdities, while established poets seek out unused and unusual words to make turgid sentiments seem new.
The subtext of this preference for exotic language is that poetry does not exist in the vernacular, the cultural, the relational. Rather, poetry lives in the academy, the Hermetic, the dead. The chief amusement that poetry offers readers now is a linguistic faddism. Observing the vogue-cycles of poetic words is good sport. "Sepulcher" is out, "moxibustion" is in.
When a sophomore writes an essay that is furious with arcane synonyms and academic jargon but which signifies nothing, I am sad because they have mistaken intellectualism for thought. When an amateur guitarist buys a $3,000 Les Paul so he can play a three-chord Eagles song for his girlfriend, I am sad because he has mistaken the tool for the effort. When parents name their child Archibald Marzipan Dewlap the Third, I am sad because the kid is going to be kicked around the playground.
Poets worry that a critique of the current poetic will necessitate a dumbing-down of their work, but let me be the first to assure you that the current poetic can't get much dumber.