The rhythmical and syntactical effects, if present, become too complicated for the human brain to process easily, if at all. I believe free verse should be enjoyable to read without taxing the brain. It's no wonder why I can't understand so much of it with the complexity involved. Often I can't even tell if it's complicated or gobbledygook. If that's not the motive then why not keep it simple.
Free verse can be beautiful and meaningful without tripping up the mind of the reader.
Free verse has become, in my opinion, too free. When lines are placed all over a page, a formidable barrier has been constructed to block any hope of understanding. Chaos takes away from, not adds to, a poem's reason to be. Or, as I suspect, it is easier to write poetry without restrictions or rules of any kind. A poem should not mean, but be.