Moving works like Steamboat Willy Mickey into the public domain helps feed the veins of creativity and inspiration of modern-day artists. A wide array of new ideas are already being formulated by artists and writers alike — imagining different uses for Mickey, and the other characters, songs, and stories, that can now be used in various mediums. Building off these works keeps the arts going.
Whether the arts will be advanced by these works becoming part of the public domain remains to be seen. In the past, and this situation, we've seen beloved characters used for untasteful derivative purposes that do nothing but allow creators to make a quick buck through crass internet monetization. Already Mickey is popping up in works that will do nothing but make the public miss the true intent of the original artform.