The modern rejection of form in poetry is part of a broader rejection of art itself, accomplished by changing the definition of art to mean something subjective when it previously meant something quite clear and specific.

An “art,” originally, was just a method of doing something effectively and a system for teaching others how to do so. Anyone with good reflexes and fighting instincts could be a successful duelist, but only someone with an actual method for fencing could be said to have the “art” of fencing. You wouldn't go to some inspired natural talent to learn how to survive a duel, because such a born genius could never teach you what he had never actually had to learn. You went to a fencing master- someone who understood the art or method of fencing and could pass that skill on to you.

So, there was an art of fishing, which meant the skill of catching fish. There was an art of painting, which meant the skill of painting well. There was an art of sculpture, an art of government, an art of war, an art of cooking. In each and every one of these cases, what made it an art was that there was a teachable method for acquiring the skill, but one that could not be quite reduced to the set perimeters of a science. If there was a completely perfect and quantifiable way to do it right, it was usually described as a science- for instance, the science of navigation. If the skill in question was not as quantifiable or objective, but still involved a teachable method, it was usually described as an art.

Everyone understood that some artists were geniuses and could display a transcendent, completely unquantifiable type of talent- but since that kind of talent transcends method and is not teachable, it was not the meaning of the word “art.”

In modern times, there were people who wanted to be able to be seen as artists even though they had never acquired any specific art. The tragic result of this artistic coup d'etat was the abandonment of form in poetry and the triumph of modernism in visual art. By turning the word “art” on its head and removing the connotation of a skill or method, people with neither training nor talent were able to appropriate the names of “artist” and “poet”- names that had always previously implied a hard-earned skill, and now imply something so subjective as to be meaningless. Many poets who don't use strict forms are in fact very talented. Many modernist artists are as well. But without any basis in a method or skill, there is no way to distinguish between the talented and the mediocre.