Time to excerpt Mark Scroggins' more nuanced discussion (to which I contributed slightly) from his blog, Culture Industry:
... I quoted Oscar Wilde "All bad poetry springs from genuine feeling" – which prompted a useful comment from Don Share: "I'm not sure if genuine feeling is the same as sentimentality, but of the latter, Richard Hugo said: 'Our reaction against the sentimentality embodied in Victorian and post-Victorian writing was so resolute writers came to believe that the further from sentimentality we got, the truer the art. That was a mistake.'" That's a good observation, & deserves as follow-up a bit more of the context of Wilde's remark (which gets quoted as if it were a free-standing aphorism, rather than a line from Gilbert in "The Critic as Artist"):
the real artist is he who proceeds, not from feeling to form, but from form to thought and passion. He does not first conceive an idea, and then say to himself, 'I will put my idea into a complex metre of fourteen lines,' but, realising the beauty of the sonnet-scheme, he conceives certain modes of music and methods of rhyme, and the mere form suggests what is to fill it and make it intellectually and emotionally complete. From time to time the world cries out against some charming artistic poet, because, to use its hackneyed and silly phrase, he has 'nothing to say.' But if he had something to say, he would probably say it, and the result would be tedious. It is just because he has no new message, that he can do beautiful work. He gains his inspiration from form, and from form purely, as an artist should. A real passion would ruin him. Whatever actually occurs is spoiled for art. All bad poetry springs from genuine feeling. To be natural is to be obvious, and to be obvious is to be inartistic.To which Ernest replies: "I wonder do you really believe what you say?" A good question – one might argue, I suppose, that by this point in the dialogue Gilbert has become rather shall we say "carried away" by his own rhetoric on behalf of a formalist insincerity, a method for the artist to "multiply his personalities."
The simplest thing to say is that "genuine feeling" – "sincerity" – is not enough to make good poetry (tho it's great for voyeuristically interesting blogs), but that poetry can be a way of embodying such genuine feeling in form – a sincere regard for which (& here I follow Zukofsky, & suspect the Divine Oscar would agree) is a necessity for successful verse.
* We always have in mind the "angel of history" via Benjamin's 9th thesis, but forget this, from the 8th: "One reason why Fascism has a chance is that in the name of progress its opponents treat it as a historical norm."