Most poetry ever written probably follows that percentage, and that definition. I'm going to make what might be a bold statement here: Most art is garbage, even the educated stuff (sometimes especially the educated stuff). Take classical music for an example (as it's my main focus). There are thousands of composers writing music right now. Maybe one of them will be remembered in 100 years. Even of the people we think of "Great 20th century composers", Copland, Shostakovich, Prokofiev, Gershwin, Shoenberg, Ellington, and others, perhaps two or three will be remembered and celebrated in the way that we remember and celebrate people like Bach and Mozart. Even then, not everything the "Masters" wrote was great- Beethoven's "Wellington's Victory" has generally been seen as awful from the moment it premiered. You have to run under the assumption that most of the art you will ever see created in your lifetime with be crap, and even the stuff that will be good will be forgotten, just like every other age. Museums can make this deceptive, showcasing the greatest art from 500 years and more, but it's not that those people didn't have to deal with crap. It's that the crap has dried up and blown away, leaving (mostly) the good stuff. So what i'm saying is that your statement is correct, but it is also correct for every other era of poetry, and every other kind of art.
The problem is that academics get to define what is crap and what isn't, and force that narrative. John Gardner blew several chapters arguing that people teach what is easy to demonstrate, not what is good, the end result being that pedantry defines a genre, not quality. And, the longer someone's been dead the less controversy there is. I had an English teacher argue that James Fenimore Cooper was art because millions of people loved his books but Stephen King was not because. And then she changed the subject. The fact that we're forced to choke down Leatherstocking bullshit purely because everyone read it back then is like arguing kids 200 years from now are gonna have to read goddamn Twilight because it was on every supermarket shelf, while arguing no one should read Twilight now because Stephanie Meyer isn't a hundred years dead. Most art is garbage. But "experts" get to elevate their garbage choices and lord their expertise over the rest of us. And we hate you for it.