Why was the everyday language in Lyrical Ballads controversial?

The use of everyday language in Lyrical Ballads was controversial because it directly challenged the established poetic diction of the late 18th century, which favored formal, "elevated," and conventional language.123

During this era, poetry was expected to adhere to specific standards of decorum, often employing "gaudy and inane" phraseology that William Wordsworth and Samuel Taylor Coleridge found stale and unsuited for expressing genuine human emotion. By choosing to write in "the language really used by men," the authors sought to democratize poetry and focus on the experiences of humble, rustic people.2314

This shift was perceived by many contemporary critics as a descent into familiarity that lacked sufficient dignity. Because the prevailing literary culture valued a more formal, generalized style, Wordsworth’s "experiments" with common speech were seen as a radical departure from artistic etiquette, sparking significant debate regarding the proper boundaries and subject matter of poetry.235