For context, the sentence immediately following the one you are asking about reads:
But that a downright simpleness, under the affectation of simplicity, prosaic words in feeble metre, silly thoughts in childish phrases, and a preference of mean, degrading, or at best trivial associations and characters, should succeed in forming a school of imitators, a company of almost religious admirers, and this too among young men of ardent minds, liberal education, and not
——with academic laurels unbestowed;
and that this bare and bald counterfeit of poetry, which is characterized as below criticism, should for nearly twenty years have well-nigh engrossed criticism, as the main, if not the only, butt of review, magazine, pamphlet, poem, and paragraph; this is indeed matter of wonder.
And an earlier question asked about the sentence immediately preceding. As an answer there states, in this section Coleridge is defending Wordsworth against long-continuing attacks. He says that it is astonishing that Wordsworth's poems, first published in 1798, should still be facing a continuous barrage of criticism. Coleridge points up a contradiction in the criticism Wordsworth has received. On the one hand, he is accused of being too plain, producing a "bare and bald counterfeit of poetry"; on the other, of being too attractive, "corrupting the people's judgment". He defends Wordsworth by contrasting him with three earlier poets: Abraham Cowley (1618–1667), Giambattista Marino (aka Giovan Battista Marini; 1569–1625), and Erasmus Darwin (1731–1802).
To paraphrase what Coleridge is saying about Wordsworth vis-à-vis the other three poets:
It would be understandable if Cowley, Marino, or Darwin were attacked for twenty years, because their poems are capable of corrupting people's tastes for even longer. But it's odd that Wordsworth has been attacked for twenty years. Unlike those other poets, he uses simple diction and focuses on ordinary people. Critics attack him precisely for this reason, saying that his poetry is not lofty enough to merit any attention. Yet if his poetry is so simplistic, how is it that Wordsworth has so many imitators and admirers among young, educated men? And even as his detractors say his poetry is beneath criticism, they cannot seem to stop talking about it!
The style and subject matter of these earlier poets is starkly different from Wordsworth's. Cowley's work is distinguished by its highly ornate, self-conscious diction, where poetic feeling is sacrificed in favor of rhetorical and intellectual flourishes. Marino's poems, while graceful, are similarly artificial and excessively reliant on elaborate conceits. And Darwin's long poem, The Botanic Garden, uses the conventional form of the heroic couplet to put forward botanical observations that furthered his theory of evolution (he was the grandfather of both Charles Darwin and Francis Galton). All three poets were very popular and well-received in their day.
Coleridge is placing the elaborate displays of Cowley, Marini, and Darwin against the simple eloquence of Wordsworth. He is suggesting that their poetry is flashy and seductive in a way that Wordsworth's is not. Echoing Quintilian on Seneca (as Gareth Rees notes), Coleridge suggests the very attractiveness of these poets make them dangerous, as it leads to a faulty understanding of what good poetry is. The relentless attacks on Wordsworth demonstrate this flawed judgment, and are therefore misguided. They would be better directed against those earlier poets.
