The antonym for the phrase "art given ones due" would be "art neglected or ignored." It refers to the unfortunate reality that some artwork, despite its value and significance, is not appreciated or recognized by its audience or the society in which it exists. Such neglect could stem from various reasons, including a lack of understanding, bias, or commercialization of art. When art is not given its due, it may fail to connect with its intended purpose or inspire the audience, leading to a diminished impact on cultural and social values. Therefore, it is vital to acknowledge and appreciate the value of art in all its forms.