Wasn't it the insistence by some to essentially equate Imagism (big I) with symbolism that led Pound to start referring to Vorticism and to abandon Imagism. I think Pound was intent on showing modernism and its subset, vorticism (imagism) as very distinct from symbolism or any of the other modes of the romantics.
This is excellent. Often the task of the poet is to _limit_ the tangle of symbols triggered by any given word or phrase; that, I think, is what is implied by the injunction ""To Purify the dialect of the tribe." Doesn't Eliot, somewhere, speak of undisciplined squads of emotions (something like that)? That archetypal bad line, "It takes a heap o' living to make a house a home," is flamboyantly "symbolic"; the reader is asked to feel every possible emotion triggered by "home."
I think Pound's discussion in ABC of Reading of Johnson's "...Human Wishes" may be relevant here.
P.S. Pound & Eliot, of course, were unfair to the Romantics. Wordsworth's "Solitary Reaper" has Shakespearean precision.