Someone on HN, don’t remember who, made the observation that some artists mistake mastery of tools for the art, whereas artists who focus on the actual art can roll with changes to the tools.
But, AI isn't just a tool, it's actually generating musical ideas at a highly finished level. For the first time, we have something that takes over a substantial amount of the creativity used to write a piece, a process which has always been the domain of people, and it's doing it at levels that are close to what the best skilled humans can do. Yeah, this isn't just something that aids creation, but is doing the creating itself.
Maybe one day, will use AI to create substantial amounts of the music I write, but am not nearly at that point yet - don't think most classical concert audiences want to got to a concert hall to hear AI generated music, but that may change. Guess we'll have to wait and see.