When it comes to opinions everyone has one. Saying that Modernist poetry has no specific structure or form and therefore means it is not as ‘effective’, is like myself saying curry is spicy, sweet and doesn’t fit in with my taste buds and therefore curry is the worst seasoning. Poetry is far too complex to reduce to a simple “effective” or “not effective” dichotomy.
To object to an opinion maybe you need to understand where they are coming from. Taking a look at traditional poetry you see rhyme schemes and specific meter and other rigid aspects of form. Modernist experimented vigorously with the poetic forms, language and versification, often doing away with rhythmical sweetness and the regularity of the traditional forms. Like a teenager that never finishes high school. She is considered by society to be a failure because she never met their ideals. However, she then goes out, gets signed and now almost everyone knows her name, Christina Aguilera.
Whatever be the structure of a modern poem, there is a hidden meaning and rhythm of course. Even, that particular structure bears significance. That beauty and meaning cannot be interpreted by traditional readers. Others, of course, prefer traditional poetry, but I do not think either is more effective than the other; they just cater to different tastes. Just like when it comes to tastes in music, some people like country others prefer rap. Just because one become before the other doesn’t make it the right one and the other wrong, it makes them different.