Near the end of The Habit of Art Bennett has Auden recite "faultlessly" some of his most famous lines, from the elegy for W.B. Yeats. Seeing the play and even more reading it, I was struck by the fact that Bennett includes three stanzas that Auden omitted in later editions of the poem ("Time that is intolerant ... Pardons him for writing well.") The stanzas, especially the third linking Yeats to Kipling and Claudel as writers whom time will pardon (for their right-wing views) because they wrote well, are pretty arrogant and probably Auden was right to drop them. I wondered why Bennett wanted them back in. But then it struck me they are what the play is about--writers/artists who are imperfect humans but great creators.
Taking that as Bennett's judgement of Auden and Britten, it's rather arrogant of him—always arrogant to sit in judgement on others, at least publicly. Though I think the most Bennett really faults Auden and Britten for are types of normal human unkindness and the seediness which can go with old age (I speak as one about to go on Medicare).
In his intro Bennett relates his play to Auden's long poem/prose work The Sea and the Mirror, even though Bennett says the latter is "(to me) impenetrable." Perhaps he would have been better off leaving it alone. The Sea and the Mirror is an "epilogue" to The Tempest which, I think, eventually suggests that the only way a work of art can really reflect reality is by being imperfect, thus mirroring the imperfection of our world and sending our thoughts towards God. There doesn't seem to be anything religious about The Habit of Art, I think Bennett's last words for his Caliban ("you want to be knowing") are untrue to the character, and the last lines about "always somebody left out" seem to want to have to do with The Sea and the Mirror but don't (Caliban escapes from dramatic resolution in The Sea and the Mirror, he isn't left out of it). (Excuse for holding forth: I'm listed as co-author, with my ex-wife Lucy, of "Artifice and Self-Consciousness in The Sea and the Mirror " [first published 1975, rpt. in Caliban, ed. Harold Bloom, 1992]—she wrote most of it.)